diff --git a/.config/dotnet-tools.json b/.config/dotnet-tools.json
index 3ba3de754..e0d46651d 100644
--- a/.config/dotnet-tools.json
+++ b/.config/dotnet-tools.json
@@ -3,7 +3,7 @@
   "isRoot": true,
   "tools": {
     "fable": {
-      "version": "3.7.20",
+      "version": "4.1.4",
       "commands": [
         "fable"
       ]
diff --git a/.github/workflows/fable.yml b/.github/workflows/fable.yml
index 99669df08..e4c036c29 100644
--- a/.github/workflows/fable.yml
+++ b/.github/workflows/fable.yml
@@ -39,7 +39,43 @@ jobs:
     - name: Run Fable tests
       working-directory: tests/FSharpPlusFable.Tests
       run: fable . --outDir bin --runScript ./bin
-  
+
+  testfable4:
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Restore
+      run: git submodule update --init --recursive
+    - name: Remove global json
+      run: rm global.json
+    - name: Setup .NET Core 7
+      uses: actions/setup-dotnet@v1
+      with:
+        dotnet-version: 7.0.200
+    - name: Setup .NET Core 6
+      uses: actions/setup-dotnet@v1
+      with:
+        dotnet-version: 6.0.201
+    - name: Restore tools
+      run: dotnet tool restore
+    - name: Install jq
+      uses: dcarbone/install-jq-action@v1.0.1
+    - name: Install fable
+      run: |
+        version=`cat ./.config/dotnet-tools.json | jq --raw-output '.tools.fable.version'`
+        dotnet tool install --global Fable --version $version
+    - name: Use Node.js
+      uses: actions/setup-node@v1
+      with:
+        node-version: '18.x'
+    - name: Install npm dependencies
+      working-directory: tests/FSharpPlusFable.Tests
+      run: npm install
+    - name: Run Fable tests
+      working-directory: tests/FSharpPlusFable.Tests
+      run: fable . --outDir bin --runScript ./bin
+
   testFable3SubsetOnCore:
     runs-on: ubuntu-latest
 
diff --git a/src/FSharpPlus/Builders.fs b/src/FSharpPlus/Builders.fs
index dd2b69f8c..0936ae1df 100644
--- a/src/FSharpPlus/Builders.fs
+++ b/src/FSharpPlus/Builders.fs
@@ -11,7 +11,7 @@ namespace FSharpPlus
 
 #nowarn "40"
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 /// Constructs to express generic computations
 [<AutoOpenAttribute>]
diff --git a/src/FSharpPlus/Control/Alternative.fs b/src/FSharpPlus/Control/Alternative.fs
index 23299b3b4..9592be0d0 100644
--- a/src/FSharpPlus/Control/Alternative.fs
+++ b/src/FSharpPlus/Control/Alternative.fs
@@ -6,7 +6,7 @@ namespace FSharpPlus.Control
 /// </summary>
 /// </namespacedoc>
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open System.Runtime.InteropServices
 open FSharpPlus
diff --git a/src/FSharpPlus/Control/Applicative.fs b/src/FSharpPlus/Control/Applicative.fs
index 6256867ae..2223d39cf 100644
--- a/src/FSharpPlus/Control/Applicative.fs
+++ b/src/FSharpPlus/Control/Applicative.fs
@@ -14,7 +14,7 @@ open FSharpPlus.Data
 type Apply =
     inherit Default1
  
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     static member inline ``<*>`` (f: '``Monad<'T->'U>``      , x: '``Monad<'T>``      , [<Optional>]_output: '``Monad<'U>``      , [<Optional>]_mthd:Default2) : '``Monad<'U>``       = Bind.InvokeOnInstance f (fun (x1: 'T->'U) -> Bind.InvokeOnInstance x (fun x2 -> Return.InvokeOnInstance (x1 x2)))
     static member inline ``<*>`` (f: '``Applicative<'T->'U>``, x: '``Applicative<'T>``, [<Optional>]_output: '``Applicative<'U>``, [<Optional>]_mthd:Default1) : '``Applicative<'U>`` = ((^``Applicative<'T->'U>`` or ^``Applicative<'T>`` or ^``Applicative<'U>``) : (static member (<*>) : _*_ -> _) f, x)
@@ -87,7 +87,7 @@ type Apply =
     static member inline InvokeOnInstance (f: '``Applicative<'T->'U>``) (x: '``Applicative<'T>``) : '``Applicative<'U>`` =
         ((^``Applicative<'T->'U>`` or ^``Applicative<'T>`` or ^``Applicative<'U>``) : (static member (<*>) : _*_ -> _) (f, x))
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type Lift2 =
     inherit Default1
diff --git a/src/FSharpPlus/Control/Arrow.fs b/src/FSharpPlus/Control/Arrow.fs
index ae4178ef3..b3abe037b 100644
--- a/src/FSharpPlus/Control/Arrow.fs
+++ b/src/FSharpPlus/Control/Arrow.fs
@@ -1,7 +1,7 @@
 namespace FSharpPlus.Control
 
 #nowarn "0077"
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open System
 open System.Runtime.InteropServices
diff --git a/src/FSharpPlus/Control/ArrowApply.fs b/src/FSharpPlus/Control/ArrowApply.fs
index cdbd66ec1..b5fd722fe 100644
--- a/src/FSharpPlus/Control/ArrowApply.fs
+++ b/src/FSharpPlus/Control/ArrowApply.fs
@@ -4,7 +4,7 @@ open System
 open System.Runtime.InteropServices
 open FSharpPlus.Internals
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 // ArrowApply class -------------------------------------------------------
 
diff --git a/src/FSharpPlus/Control/ArrowChoice.fs b/src/FSharpPlus/Control/ArrowChoice.fs
index 214dfde96..a4da4bc43 100644
--- a/src/FSharpPlus/Control/ArrowChoice.fs
+++ b/src/FSharpPlus/Control/ArrowChoice.fs
@@ -1,7 +1,7 @@
 namespace FSharpPlus.Control
 
 #nowarn "0077"
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open System
 open System.Runtime.InteropServices
diff --git a/src/FSharpPlus/Control/Bifoldable.fs b/src/FSharpPlus/Control/Bifoldable.fs
index e6d746b2f..384e535e7 100644
--- a/src/FSharpPlus/Control/Bifoldable.fs
+++ b/src/FSharpPlus/Control/Bifoldable.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Control
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open System.Runtime.InteropServices
 open FSharpPlus.Internals
diff --git a/src/FSharpPlus/Control/Bitraversable.fs b/src/FSharpPlus/Control/Bitraversable.fs
index 2157044ed..7c08aa72c 100644
--- a/src/FSharpPlus/Control/Bitraversable.fs
+++ b/src/FSharpPlus/Control/Bitraversable.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Control
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 // open System.Runtime.InteropServices
 open FSharpPlus.Internals
diff --git a/src/FSharpPlus/Control/Category.fs b/src/FSharpPlus/Control/Category.fs
index 2cf8563f4..9cfe4657d 100644
--- a/src/FSharpPlus/Control/Category.fs
+++ b/src/FSharpPlus/Control/Category.fs
@@ -1,7 +1,7 @@
 namespace FSharpPlus.Control
 
 #nowarn "0077"
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open System
 open System.Runtime.InteropServices
diff --git a/src/FSharpPlus/Control/Collection.fs b/src/FSharpPlus/Control/Collection.fs
index a6dfd58da..580e9b69f 100644
--- a/src/FSharpPlus/Control/Collection.fs
+++ b/src/FSharpPlus/Control/Collection.fs
@@ -8,7 +8,7 @@ open System.Runtime.InteropServices
 open FSharpPlus
 open FSharpPlus.Internals
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type OfSeq =
     inherit Default1
diff --git a/src/FSharpPlus/Control/Comonad.fs b/src/FSharpPlus/Control/Comonad.fs
index 80959abd9..d8575eb60 100644
--- a/src/FSharpPlus/Control/Comonad.fs
+++ b/src/FSharpPlus/Control/Comonad.fs
@@ -6,13 +6,13 @@ open System.Threading.Tasks
 
 open FSharpPlus
 open FSharpPlus.Internals
-
+#if !FABLE_COMPILER4
 
 // Comonad class ----------------------------------------------------------
 
 type Extract =
     static member        Extract (x: Async<'T>    ) =
-    #if FABLE_COMPILER_3
+    #if FABLE_COMPILER_3 || FABLE_COMPILER_4
         Async.RunSynchronously x
     #else
         Async.StartImmediateAsTask(x).Result
@@ -118,3 +118,4 @@ type Duplicate =
         call (Unchecked.defaultof<Duplicate>, x, Unchecked.defaultof<'``Comonad<'Comonad<'T>>``>)
 
 #endif
+#endif
\ No newline at end of file
diff --git a/src/FSharpPlus/Control/Converter.fs b/src/FSharpPlus/Control/Converter.fs
index 02cfe7609..c3398f45a 100644
--- a/src/FSharpPlus/Control/Converter.fs
+++ b/src/FSharpPlus/Control/Converter.fs
@@ -10,7 +10,7 @@ open System.Text
 open FSharpPlus.Internals
 open FSharpPlus.Internals.Prelude
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type Explicit =
     inherit Default1
diff --git a/src/FSharpPlus/Control/Foldable.fs b/src/FSharpPlus/Control/Foldable.fs
index ab138d6ea..60f4dc1c2 100644
--- a/src/FSharpPlus/Control/Foldable.fs
+++ b/src/FSharpPlus/Control/Foldable.fs
@@ -4,7 +4,7 @@
 // Warn FS0077 -> Member constraints with the name 'get_Item' are given special status by the F# compiler as certain .NET types are implicitly augmented with this member. This may result in runtime failures if you attempt to invoke the member constraint from your own code.
 // Those .NET types are string and array. String is explicitely handled here and array through the seq overload.
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open FSharpPlus.Control
 
diff --git a/src/FSharpPlus/Control/Functor.fs b/src/FSharpPlus/Control/Functor.fs
index 28972099c..ffa4ae93b 100644
--- a/src/FSharpPlus/Control/Functor.fs
+++ b/src/FSharpPlus/Control/Functor.fs
@@ -13,7 +13,7 @@ open FSharpPlus.Internals.Prelude
 open FSharpPlus
 open FSharpPlus.Data
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && ! FABLE_COMPILER_4
 
 // Functor class ----------------------------------------------------------
 
@@ -61,7 +61,7 @@ type Iterate =
 type Map =
     inherit Default1
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     static member Map ((x: Lazy<_>             , f: 'T->'U), _mthd: Map) = Lazy.map f x
     #if !FABLE_COMPILER
@@ -113,7 +113,7 @@ type Map =
     static member inline InvokeOnInstance (mapping: 'T->'U) (source: '``Functor<'T>``) : '``Functor<'U>`` = 
         (^``Functor<'T>`` : (static member Map : _ * _ -> _) source, mapping)
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 
 type Map with
@@ -139,7 +139,7 @@ type Map with
     static member inline Map ((_: ^t when ^t: null and ^t: struct, _ ), _mthd: Default1) = ()
 
 #endif
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type Unzip =
     inherit Default1
@@ -199,7 +199,7 @@ type Unzip =
         call (Unchecked.defaultof<Unzip>, source) : '``Functor<'T1>`` * '``Functor<'T2>``
 
 #endif
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type Zip =
     inherit Default1
@@ -239,7 +239,7 @@ type Zip with
     static member inline Zip ((x: '``ZipFunctor<'T1>``            , y: '``ZipFunctor<'T2>``            , _output: '``ZipFunctor<'T1 * 'T2>``      ), _mthd: Default1) = Zip.InvokeOnInstance x y : '``ZipFunctor<'T1 * 'T2>``
 
 #endif
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 // Bifunctor class --------------------------------------------------------
 
@@ -260,7 +260,7 @@ type Bimap =
         (^``Bifunctor<'T,'V>``: (static member Bimap : _*_*_ -> _) source, f, g)
 
 #endif
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type MapFirst =
     inherit Default1
@@ -312,7 +312,7 @@ type Dimap =
         (^``Profunctor<'B,'C>`` : (static member Dimap : _*_*_ -> _) source, ab, cd)
 
 #endif
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 // Contravariant class ----------------------------------------------------
 
@@ -338,7 +338,7 @@ type Contramap =
     #endif
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     
 type Contramap with
     static member inline Contramap (x: '``Profunctor<'B,'C>``, f: 'A->'B, [<Optional>]_mthd: Default2) = Dimap.InvokeOnInstance f id x : '``Profunctor<'A,'C>``
@@ -346,13 +346,13 @@ type Contramap with
     static member inline Contramap (_: ^t when ^t: null and ^t: struct  , _: 'A->'B,  _mthd: Default1) = ()
 
 #endif
-#if !FABLE_COMPILER|| FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type Map with
     static member inline Map ((x: '``Profunctor<'B,'C>``, cd: 'C->'D), [<Optional>]_mthd: Default5) = Dimap.InvokeOnInstance id cd x : '``Profunctor<'B,'D>``
 
 #endif
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type Dimap with
     static member inline Dimap (x: '``Profunctor<'B,'C>``, ab: 'A->'B, cd: 'C->'D, [<Optional>]_mthd: Default2) = x |> Map.InvokeOnInstance cd |> Contramap.InvokeOnInstance ab : '``Profunctor<'A,'D>``
diff --git a/src/FSharpPlus/Control/Indexable.fs b/src/FSharpPlus/Control/Indexable.fs
index 0884c115b..d3882dea6 100644
--- a/src/FSharpPlus/Control/Indexable.fs
+++ b/src/FSharpPlus/Control/Indexable.fs
@@ -4,7 +4,7 @@
 // Warn FS0077 -> Member constraints with the name 'get_Item' are given special status by the F# compiler as certain .NET types are implicitly augmented with this member. This may result in runtime failures if you attempt to invoke the member constraint from your own code.
 // Those .NET types are string and array but they are explicitely handled here.
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open System
 open System.Runtime.InteropServices
diff --git a/src/FSharpPlus/Control/Invokable.fs b/src/FSharpPlus/Control/Invokable.fs
index 13fd2728b..0eba3b723 100644
--- a/src/FSharpPlus/Control/Invokable.fs
+++ b/src/FSharpPlus/Control/Invokable.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Control
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open System
 open FSharpPlus.Internals
diff --git a/src/FSharpPlus/Control/Monad.fs b/src/FSharpPlus/Control/Monad.fs
index 89635d765..15ff7be77 100644
--- a/src/FSharpPlus/Control/Monad.fs
+++ b/src/FSharpPlus/Control/Monad.fs
@@ -12,7 +12,7 @@ open FSharpPlus.Data
 open FSharpPlus.Internals
 open FSharpPlus.Internals.Prelude
 
-
+#if !FABLE_COMPILER_4
 // Monad class ------------------------------------------------------------
 
 type Bind =
@@ -128,7 +128,7 @@ type Return =
     inherit Default1
     static member inline InvokeOnInstance (x: 'T) = (^``Applicative<'T>`` : (static member Return : ^T -> ^``Applicative<'T>``) x)
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     static member inline Invoke (x: 'T) : '``Applicative<'T>`` =
         let inline call (mthd: ^M, output: ^R) = ((^M or ^R) : (static member Return : _*_ -> _) output, mthd)
@@ -329,3 +329,4 @@ type Using with
     static member inline Using (_                                  , _   : 'a -> ^t when ^t : null and ^t: struct               , _: Using   ) = ()
 
 #endif
+#endif
diff --git a/src/FSharpPlus/Control/MonadOps.fs b/src/FSharpPlus/Control/MonadOps.fs
index 48970ced1..9e7409f20 100644
--- a/src/FSharpPlus/Control/MonadOps.fs
+++ b/src/FSharpPlus/Control/MonadOps.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Internals
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 module internal MonadOps =
     open FSharpPlus.Control
diff --git a/src/FSharpPlus/Control/MonadTrans.fs b/src/FSharpPlus/Control/MonadTrans.fs
index ec20c437c..0f40ac319 100644
--- a/src/FSharpPlus/Control/MonadTrans.fs
+++ b/src/FSharpPlus/Control/MonadTrans.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Control
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open FSharpPlus
 
diff --git a/src/FSharpPlus/Control/Monoid.fs b/src/FSharpPlus/Control/Monoid.fs
index 35adb4262..a91b65849 100644
--- a/src/FSharpPlus/Control/Monoid.fs
+++ b/src/FSharpPlus/Control/Monoid.fs
@@ -12,7 +12,7 @@ open FSharpPlus.Data
 open FSharpPlus.Internals
 open FSharpPlus.Internals.Prelude
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 [<Extension; Sealed>]
 type Plus =
diff --git a/src/FSharpPlus/Control/Numeric.fs b/src/FSharpPlus/Control/Numeric.fs
index 2146481d3..55e2bea8c 100644
--- a/src/FSharpPlus/Control/Numeric.fs
+++ b/src/FSharpPlus/Control/Numeric.fs
@@ -42,7 +42,7 @@ type FromBigInt =
         call Unchecked.defaultof<FromBigInt> x
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type FromInt64 =
     inherit Default1
diff --git a/src/FSharpPlus/Control/Traversable.fs b/src/FSharpPlus/Control/Traversable.fs
index 5fd04e3a8..f977aad99 100644
--- a/src/FSharpPlus/Control/Traversable.fs
+++ b/src/FSharpPlus/Control/Traversable.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Control
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open System.Runtime.InteropServices
 open System.ComponentModel
diff --git a/src/FSharpPlus/Control/Tuple.fs b/src/FSharpPlus/Control/Tuple.fs
index 0cc1564b9..a29772af7 100644
--- a/src/FSharpPlus/Control/Tuple.fs
+++ b/src/FSharpPlus/Control/Tuple.fs
@@ -161,7 +161,7 @@ type MapItem5 =
         call (Unchecked.defaultof<MapItem5>, value)
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 type Curry =
     static member inline Invoke f =
diff --git a/src/FSharpPlus/Data/Cont.fs b/src/FSharpPlus/Data/Cont.fs
index 9aec5f299..1b2296d75 100644
--- a/src/FSharpPlus/Data/Cont.fs
+++ b/src/FSharpPlus/Data/Cont.fs
@@ -90,7 +90,7 @@ type Cont<'r,'t> with
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member CallCC (f: ('T -> Cont<'R,'U>) -> _) = Cont.callCC f : Cont<'R,'T>
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     static member inline Lift (m: '``Monad<'T>``) = Cont ((>>=) m) : ContT<'``Monad<'R>``,'T>
 
diff --git a/src/FSharpPlus/Data/Coproduct.fs b/src/FSharpPlus/Data/Coproduct.fs
index 9dc662945..4385c44f9 100644
--- a/src/FSharpPlus/Data/Coproduct.fs
+++ b/src/FSharpPlus/Data/Coproduct.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Data
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open FSharpPlus
 open FSharpPlus.Control
diff --git a/src/FSharpPlus/Data/Error.fs b/src/FSharpPlus/Data/Error.fs
index a226b59df..125fd1d83 100644
--- a/src/FSharpPlus/Data/Error.fs
+++ b/src/FSharpPlus/Data/Error.fs
@@ -7,7 +7,7 @@ open FSharpPlus.Internals.Prelude
 open FSharpPlus.Control
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 /// Additional operations on Result
 [<RequireQualifiedAccess>]
 module Result =
@@ -30,7 +30,7 @@ module ResultOrException =
     let Exception : Result<_,exn>   -> _ = function Error e -> e | _ -> exn ()
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 /// Monad Transformer for Result<'T, 'E>
 [<Struct>]
diff --git a/src/FSharpPlus/Data/Kleisli.fs b/src/FSharpPlus/Data/Kleisli.fs
index 067197909..20f67275b 100644
--- a/src/FSharpPlus/Data/Kleisli.fs
+++ b/src/FSharpPlus/Data/Kleisli.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Data
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open FSharpPlus
 open FSharpPlus.Control
diff --git a/src/FSharpPlus/Data/List.fs b/src/FSharpPlus/Data/List.fs
index 814cfa892..e75361ca6 100644
--- a/src/FSharpPlus/Data/List.fs
+++ b/src/FSharpPlus/Data/List.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Data
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open FSharpPlus
 open System.ComponentModel
diff --git a/src/FSharpPlus/Data/Monoids.fs b/src/FSharpPlus/Data/Monoids.fs
index 8a92bd8de..69da14a38 100644
--- a/src/FSharpPlus/Data/Monoids.fs
+++ b/src/FSharpPlus/Data/Monoids.fs
@@ -1,10 +1,9 @@
 namespace FSharpPlus.Data
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
-
 open FSharpPlus
 open FSharpPlus.Internals.Prelude
 
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 /// The dual of a monoid, obtained by swapping the arguments of append.
 [<Struct>]
 type Dual<'t> = Dual of 't with
@@ -41,7 +40,7 @@ type Any = Any of bool with
     static member (+) (Any x, Any y) = Any (x || y)
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 /// <summary> The Const functor, defined as Const&lt;&#39;T, &#39;U&gt; where &#39;U is a phantom type. Useful for: Lens getters Its applicative instance plays a fundamental role in Lens.
 /// <para/>   Useful for: Lens getters.
@@ -129,7 +128,7 @@ type Last<'t> = Last of Option<'t> with
     static member run (Last a) = a                                            : 't option
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 /// Numeric wrapper for multiplication monoid (*, 1)
 [<Struct>]
diff --git a/src/FSharpPlus/Data/NonEmptyList.fs b/src/FSharpPlus/Data/NonEmptyList.fs
index 772cba39c..a19944d37 100644
--- a/src/FSharpPlus/Data/NonEmptyList.fs
+++ b/src/FSharpPlus/Data/NonEmptyList.fs
@@ -129,7 +129,7 @@ module NonEmptyList =
         | []   -> {Head = s; Tail = []}
         | h::t -> cons s (tails {Head = h; Tail = t})
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     /// <summary>
     /// Maps each element of the list to an action, evaluates these actions from left to right and collect the results.
@@ -200,7 +200,7 @@ module NonEmptyList =
     /// Equivalent to [start..stop] on regular lists.
     let inline range (start: 'T) stop = create start (List.drop 1 [start..stop])
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     /// Reduces using alternative operator `<|>`.
     let inline choice (list: NonEmptyList<'``Alt<'T>``>) = reduce (<|>) list : '``Alt<'T>``
 #endif
@@ -244,7 +244,7 @@ type NonEmptyList<'t> with
 
     static member Extract   {Head = h; Tail = _} = h : 't
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     static member Duplicate (s: NonEmptyList<'a>, [<Optional>]_impl: Duplicate) = NonEmptyList.tails s
     #endif
 
@@ -257,7 +257,7 @@ type NonEmptyList<'t> with
     static member FoldBack ({Head = x; Tail = xs}, f, z) = List.foldBack f (x::xs) z
     static member Sum (source: seq<NonEmptyList<'T>>) = source |> Seq.map NonEmptyList.toList |> List.concat |> NonEmptyList.ofList
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member ToList (s: NonEmptyList<'a>, [<Optional>]_impl: ToList) = NonEmptyList.toList s    
 
diff --git a/src/FSharpPlus/Data/NonEmptyMap.fs b/src/FSharpPlus/Data/NonEmptyMap.fs
index bc08c9462..406b98241 100644
--- a/src/FSharpPlus/Data/NonEmptyMap.fs
+++ b/src/FSharpPlus/Data/NonEmptyMap.fs
@@ -246,7 +246,7 @@ module NonEmptyMap =
     /// Returns the union of two maps, preferring values from the first in case of duplicate keys.
     let union (source: NonEmptyMap<'Key, 'T>) (altSource: NonEmptyMap<'Key, 'T>) = unionWith (fun x _ -> x) source altSource
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     let inline traverse (f: 'T->'``Functor<'U>``) (m: NonEmptyMap<'K, 'T>) : '``Functor<NonEmptyMap<'K, 'U>>`` =
         let m' = traverse f (toMap m) : '``Functor<Map<'K, 'U>>``
         ofMap <!> m' : '``Functor<NonEmptyMap<'K, 'U>>``
@@ -266,7 +266,7 @@ type NonEmptyMap<[<EqualityConditionalOn>]'Key,[<EqualityConditionalOn;Compariso
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member Unzip (x: NonEmptyMap<'K, ('T * 'U)>) = NonEmptyMap.unzip x : NonEmptyMap<'K, 'T> * NonEmptyMap<'K, 'U>
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member inline Traverse (x: NonEmptyMap<'K, 'T>, f: 'T->'``Functor<'U>``) : '``Functor<NonEmptyMap<'K, 'U>>`` = NonEmptyMap.traverse f x
 
diff --git a/src/FSharpPlus/Data/NonEmptySet.fs b/src/FSharpPlus/Data/NonEmptySet.fs
index 0bce60fec..c3b1f620b 100644
--- a/src/FSharpPlus/Data/NonEmptySet.fs
+++ b/src/FSharpPlus/Data/NonEmptySet.fs
@@ -235,7 +235,7 @@ type NonEmptySet<[<EqualityConditionalOn>]'a when 'a: comparison> with
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member FoldBack (set: NonEmptySet<'a>, f, z) = Set.foldBack f set.Value z
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member ToList (s: NonEmptySet<'a>, [<Optional>]_impl: ToList) = NonEmptySet.toList s
 
diff --git a/src/FSharpPlus/Data/Option.fs b/src/FSharpPlus/Data/Option.fs
index 7935d333b..aadb747b0 100644
--- a/src/FSharpPlus/Data/Option.fs
+++ b/src/FSharpPlus/Data/Option.fs
@@ -6,7 +6,7 @@ open FSharpPlus.Internals.Prelude
 open FSharpPlus.Control
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 /// Additional operations on Option
 [<RequireQualifiedAccess>]
diff --git a/src/FSharpPlus/Data/Reader.fs b/src/FSharpPlus/Data/Reader.fs
index 3879f6f78..c14deaa4d 100644
--- a/src/FSharpPlus/Data/Reader.fs
+++ b/src/FSharpPlus/Data/Reader.fs
@@ -76,7 +76,7 @@ type Reader<'r,'t> with
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member Local (m, f: 'R1->'R2) = Reader.local f m      : Reader<'R1,'T>
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member Zip (x, y) = Reader.zip x y
 
@@ -91,7 +91,7 @@ type Reader<'r,'t> with
     static member Delay (body: unit->Reader<'R,'T>)  = Reader (fun s -> Reader.run (body ()) s) : Reader<'R,'T>
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 /// Monad Transformer for Reader<'R, 'T>
 [<Struct>]
diff --git a/src/FSharpPlus/Data/Seq.fs b/src/FSharpPlus/Data/Seq.fs
index d552d9056..33850ffd9 100644
--- a/src/FSharpPlus/Data/Seq.fs
+++ b/src/FSharpPlus/Data/Seq.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus.Data
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open System.ComponentModel
 open FSharpPlus
diff --git a/src/FSharpPlus/Data/State.fs b/src/FSharpPlus/Data/State.fs
index 8a28e223f..ae09e37b6 100644
--- a/src/FSharpPlus/Data/State.fs
+++ b/src/FSharpPlus/Data/State.fs
@@ -94,7 +94,7 @@ type State<'s,'t> with
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member Put x     = State.put x                      : State<'S,unit>
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member Zip (x, y) = State.zip x y
     #endif
@@ -105,7 +105,7 @@ type State<'s,'t> with
     static member Delay (body: unit->State<'S,'T>)  = State (fun s -> State.run (body ()) s) : State<'S,'T>
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open FSharpPlus.Control
 open FSharpPlus.Internals.Prelude
diff --git a/src/FSharpPlus/Data/Validation.fs b/src/FSharpPlus/Data/Validation.fs
index 42906d4e4..ab2513d31 100644
--- a/src/FSharpPlus/Data/Validation.fs
+++ b/src/FSharpPlus/Data/Validation.fs
@@ -5,7 +5,7 @@ namespace FSharpPlus.Data
 open System.ComponentModel
 open FSharpPlus
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 open FSharpPlus.Lens
 #endif
 
@@ -89,7 +89,7 @@ module Validation =
         | Success a -> folder a state
         | Failure _ -> state
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     /// Traverse the Success case with the supplied function.
     let inline traverse (f: 'T -> '``Functor<'U>``) (source: Validation<'Error, 'T>) : '``Functor<Validation<'Error, 'U>>`` =
@@ -196,7 +196,7 @@ module Validation =
     [<System.Obsolete("This function will not be supported in future versions.")>]
     let validate (e: 'e) (p: 'a -> bool) (a: 'a) : Validation<'e,'a> = if p a then Success a else Failure e
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     /// validationNel : Result<'a,'e> -> Validation (NonEmptyList<'e>) a
     /// This is 'liftError' specialized to 'NonEmptyList', since
     /// they are a common semigroup to use.
@@ -218,7 +218,7 @@ module Validation =
     let inline _Success x = (prism Success <| either Ok (Error << Failure)) x
     let inline _Failure x = (prism Failure <| either (Error << Failure) Ok) x
     #endif
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     let inline isoValidationResult x = x |> iso toResult ofResult
     #endif
     
@@ -270,7 +270,7 @@ type Validation<'error, 't> with
     static member inline Lift3 (f, x: Validation<'Error, 'T>, y: Validation<_, 'U>, z: Validation<_, 'V>) : Validation<_, 'W> = Validation.map3 f x y z
 
     // as Alternative (inherits from Applicative)
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     static member inline get_Empty () = Failure (getEmpty ())
     static member inline (<|>) (x: Validation<'Error, 'T>, y: Validation<_,_>) = Validation.appValidation Control.Append.Invoke x y
     #endif
@@ -289,7 +289,7 @@ type Validation<'error, 't> with
     [<EditorBrowsable(EditorBrowsableState.Never)>]
     static member Bimap (x: Validation<'T, 'V>, f: 'T -> 'U, g: 'V -> 'W) : Validation<'U, 'W> = Validation.bimap f g x
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     // as Traversable
     [<EditorBrowsable(EditorBrowsableState.Never)>]
diff --git a/src/FSharpPlus/Data/ValueOption.fs b/src/FSharpPlus/Data/ValueOption.fs
index e698a2370..fb7b42719 100644
--- a/src/FSharpPlus/Data/ValueOption.fs
+++ b/src/FSharpPlus/Data/ValueOption.fs
@@ -6,7 +6,7 @@ open FSharpPlus.Internals.Prelude
 open FSharpPlus.Control
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 /// Additional operations on ValueOption
 [<RequireQualifiedAccess>]
diff --git a/src/FSharpPlus/Data/Writer.fs b/src/FSharpPlus/Data/Writer.fs
index 1b1109d94..80748a958 100644
--- a/src/FSharpPlus/Data/Writer.fs
+++ b/src/FSharpPlus/Data/Writer.fs
@@ -22,7 +22,7 @@ module Writer =
     let map f (Writer (a: 'T, w)) = Writer (f a, w)                                            : Writer<'Monoid,'U>
 
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     /// Combines two Writers into one by applying a mapping function.
     let inline map2 f (Writer (a: 'T, w1)) (Writer (b: 'U, w2)) = Writer (f a b, w1 ++ w2) : Writer<'Monoid,'V>
@@ -106,7 +106,7 @@ type Writer<'monoid,'t> with
     static member        Extract (Writer (_: 'W, a: 'T)) = a
     static member        (=>>)   (Writer (w: 'W, _: 'T) as g, f : Writer<_,_> -> 'U) = Writer (w, f g)
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 
 /// Monad Transformer for Writer<'Monoid, 'T>
diff --git a/src/FSharpPlus/Data/ZipList.fs b/src/FSharpPlus/Data/ZipList.fs
index 4f89515ea..72d5c5fb0 100644
--- a/src/FSharpPlus/Data/ZipList.fs
+++ b/src/FSharpPlus/Data/ZipList.fs
@@ -53,7 +53,7 @@ type ZipList<'s> with
 
     static member ToSeq (ZipList x) = x
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     static member inline get_Zero () = result (getZero ()) : ZipList<'a>
     static member inline (+) (x: ZipList<'a>, y: ZipList<'a>) = lift2 plus x y : ZipList<'a>
diff --git a/src/FSharpPlus/Extensions/Array.fs b/src/FSharpPlus/Extensions/Array.fs
index 05a163d4d..b70e57acf 100644
--- a/src/FSharpPlus/Extensions/Array.fs
+++ b/src/FSharpPlus/Extensions/Array.fs
@@ -150,7 +150,7 @@ module Array =
     /// <returns>
     /// The index of the slice.
     /// </returns>
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     /// <summary>
     /// Returns the index of the first occurrence of the specified slice in the source.
diff --git a/src/FSharpPlus/Extensions/Enumerator.fs b/src/FSharpPlus/Extensions/Enumerator.fs
index 6bd7068da..f681dfc44 100644
--- a/src/FSharpPlus/Extensions/Enumerator.fs
+++ b/src/FSharpPlus/Extensions/Enumerator.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 /// Additional operations on IEnumerator
 [<RequireQualifiedAccess>]
diff --git a/src/FSharpPlus/Extensions/List.fs b/src/FSharpPlus/Extensions/List.fs
index 6e9a09022..b11cf15d6 100644
--- a/src/FSharpPlus/Extensions/List.fs
+++ b/src/FSharpPlus/Extensions/List.fs
@@ -77,7 +77,7 @@ module List =
     ///
     /// <returns>List with values returned from mapping function.</returns>
     let lift3 f x1 x2 x3 =
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if !FABLE_COMPILER || FABLE_COMPILER_3 || FABLE_COMPILER_4
         List.allPairs x2 x3
         |> List.allPairs x1
         |> List.map (fun x -> (fst (snd x), snd (snd x), fst x))
@@ -243,7 +243,7 @@ module List =
             member _.GetEnumerator () = (source :> _ seq).GetEnumerator ()
             member _.GetEnumerator () = (source :> System.Collections.IEnumerable).GetEnumerator () }
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     /// <summary>
     /// Gets the index of the first occurrence of the specified slice in the source.
diff --git a/src/FSharpPlus/Extensions/Seq.fs b/src/FSharpPlus/Extensions/Seq.fs
index 44f1e3a10..a51e6eea9 100644
--- a/src/FSharpPlus/Extensions/Seq.fs
+++ b/src/FSharpPlus/Extensions/Seq.fs
@@ -203,7 +203,7 @@ module Seq =
     /// <returns>The seq converted to a System.Collections.Generic.IReadOnlyList</returns>
     let toIReadOnlyList (source: seq<_>) = source |> ResizeArray |> ReadOnlyCollection :> IReadOnlyList<_>
     #endif
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     /// <summary>
     /// Gets the index of the first occurrence of the specified slice in the source.
     /// </summary>
diff --git a/src/FSharpPlus/FSharpPlus.fsproj b/src/FSharpPlus/FSharpPlus.fsproj
index dd139e99f..9202db334 100644
--- a/src/FSharpPlus/FSharpPlus.fsproj
+++ b/src/FSharpPlus/FSharpPlus.fsproj
@@ -24,6 +24,7 @@
     <LangVersion>6.0</LangVersion>
     <DefineConstants Condition=" '$(Configuration)' == 'Fable'">$(DefineConstants);FABLE_COMPILER</DefineConstants>
     <DefineConstants Condition=" '$(Configuration)' == 'Fable3'">$(DefineConstants);FABLE_COMPILER;FABLE_COMPILER_3</DefineConstants>
+    <DefineConstants Condition=" '$(Configuration)' == 'Fable4'">$(DefineConstants);FABLE_COMPILER;FABLE_COMPILER_4</DefineConstants>
     <TargetFrameworks>netstandard2.0;netstandard2.1</TargetFrameworks>
     <!--<OutputPath>..\..\bin</OutputPath>-->
   </PropertyGroup>
diff --git a/src/FSharpPlus/Internals.fs b/src/FSharpPlus/Internals.fs
index 646b0d4bf..5f0a7a90b 100644
--- a/src/FSharpPlus/Internals.fs
+++ b/src/FSharpPlus/Internals.fs
@@ -322,7 +322,7 @@ type BitConverter =
         if isNull value then nullArg "value"
         BitConverter.ToString (value, startIndex, value.Length - startIndex)
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 // findSliceIndex
 module FindSliceIndex =
     open System.Collections.Generic
diff --git a/src/FSharpPlus/Lens.fs b/src/FSharpPlus/Lens.fs
index cf74089fb..b4e992a00 100644
--- a/src/FSharpPlus/Lens.fs
+++ b/src/FSharpPlus/Lens.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 open FSharpPlus.Operators
 open FSharpPlus.Data
diff --git a/src/FSharpPlus/Operators.fs b/src/FSharpPlus/Operators.fs
index b76ec9d42..0501efa6a 100644
--- a/src/FSharpPlus/Operators.fs
+++ b/src/FSharpPlus/Operators.fs
@@ -29,7 +29,7 @@ module Operators =
     /// <category index="0">Common Combinators</category>
     let inline uncurry f (x: 'T1, y: 'T2) : 'Result = f x y
     
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     /// <summary>
     /// Takes a function expecting a tuple of any N number of elements and returns a function expecting N curried arguments.
     /// </summary>
@@ -116,7 +116,7 @@ module Operators =
     /// <category index="0">Common Combinators</category>
     let inline tuple8<'T1, 'T2, 'T3, 'T4, 'T5, 'T6, 'T7, 'T8> (t1: 'T1) (t2: 'T2) (t3: 'T3) (t4: 'T4) (t5: 'T5) (t6: 'T6) (t7: 'T7) (t8: 'T8) = t1, t2, t3, t4, t5, t6, t7, t8
          
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     // Functor ----------------------------------------------------------------
 
@@ -389,7 +389,7 @@ module Operators =
     let inline invmap (f: 'T -> 'U) (g: 'U -> 'T) (source: '``InvariantFunctor<'T>``) = Invmap.Invoke f g source : '``InvariantFunctor<'U>``
 
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     // Category ---------------------------------------------------------------
 
@@ -1315,7 +1315,7 @@ module Operators =
     let inline mapItem5 (mapping: 'T -> 'U) (tuple: '``('A * 'B * 'C * 'D * 'T * ..)``) = MapItem5.Invoke mapping tuple : '``('A * 'B * 'C * 'D * 'U * ..)``
     
     
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     
     // Converter
 
@@ -1361,7 +1361,7 @@ module Operators =
 
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     /// <summary>
     /// Converts to a value from its string representation.
@@ -1510,7 +1510,7 @@ module Operators =
 
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     // Additional functions
 
@@ -1559,7 +1559,7 @@ module Operators =
     let dispose (resource: System.IDisposable) = match resource with null -> () | x -> x.Dispose ()
 
     
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
     /// <summary>Additional operators for Arrows related functions which shadows some F# operators for bitwise functions.</summary>
     module Arrows =
diff --git a/src/FSharpPlus/Parsing.fs b/src/FSharpPlus/Parsing.fs
index 32b08cb0e..392e5117e 100644
--- a/src/FSharpPlus/Parsing.fs
+++ b/src/FSharpPlus/Parsing.fs
@@ -1,6 +1,6 @@
 namespace FSharpPlus
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 
 [<AutoOpen>]
 module Parsing =
diff --git a/tests/FSharpPlusFable.Tests/FSharpPlusFable.Tests.fsproj b/tests/FSharpPlusFable.Tests/FSharpPlusFable.Tests.fsproj
index b84021a05..5e3daf83c 100644
--- a/tests/FSharpPlusFable.Tests/FSharpPlusFable.Tests.fsproj
+++ b/tests/FSharpPlusFable.Tests/FSharpPlusFable.Tests.fsproj
@@ -7,6 +7,7 @@
     <LangVersion Condition=" '$(Configuration)' == 'Fable' OR '$(Configuration)' == 'Fable3' ">6.0</LangVersion>
     <DefineConstants Condition=" '$(Configuration)' == 'Fable'">$(DefineConstants);FABLE_COMPILER;FABLE_COMPILER_FAKE</DefineConstants>
     <DefineConstants Condition=" '$(Configuration)' == 'Fable3'">$(DefineConstants);FABLE_COMPILER;FABLE_COMPILER_3;FABLE_COMPILER_FAKE</DefineConstants>
+    <DefineConstants Condition=" '$(Configuration)' == 'Fable4'">$(DefineConstants);FABLE_COMPILER;FABLE_COMPILER_4;FABLE_COMPILER_FAKE</DefineConstants>
     <TargetFramework>net6.0</TargetFramework>
   </PropertyGroup>
 
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/Extensions.fs b/tests/FSharpPlusFable.Tests/FSharpTests/Extensions.fs
index 57abc62dc..bc824536d 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/Extensions.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/Extensions.fs
@@ -46,7 +46,7 @@ let ExtensionsTest =
                    let r2 = m1 |> Map.unionWith konst m2
                    equalMap r1 r2)
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
       testCase "Bind" 
         (fun () ->  let x = [1;2] >>= fun x -> [string x ; string (x + 1000) ]
                     let y = { Head = 1; Tail = [2] } >>= fun x -> { Head = string x ; Tail = [string (x + 1000)] }
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General.fs
index fe7e0757f..c23fc6b14 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General.fs
@@ -158,7 +158,7 @@ let monadTransformers = testList "MonadTransformers" [
     #endif
     ]
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 module ProfunctorDefaults =
     type Fun<'T,'U> = Fun of ('T -> 'U) with
         static member Dimap ((Fun f): Fun<'B,'C>, g: 'A->'B, h:'C->'D) = Fun (g >> f >> h)
@@ -169,7 +169,7 @@ module ProfunctorDefaults =
     ()
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 module BifunctorDefaults =
     type Tup<'a,'b> = Tup of ('a * 'b) with
         static member Bimap (Tup (a, b), f, g) = Tup (f a, g b)
@@ -180,7 +180,7 @@ module BifunctorDefaults =
     ()
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 type StringCodec<'t> = StringCodec of ReaderT<string, Result<'t,string>> * ('t -> Const<string, unit>) with
     static member Invmap (StringCodec (d, e), f: 'T -> 'U, g: 'U -> 'T) = StringCodec (map f d, contramap g e)
 module StringCodec =
@@ -189,7 +189,7 @@ module StringCodec =
 #endif
 
 let invariant = testList "Invariant" [
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "testStringToIntDerivedFromFloat" (fun () ->
         let floatCodec = StringCodec (ReaderT (tryParse >> Option.toResultWith "Parse error"), string<float> >> Const)
         let floatParsed  = StringCodec.decode floatCodec "1.8"
@@ -234,7 +234,7 @@ let bitConverter = testList "BitConverter" [
 
 let curry = testList "Curry" [
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "curryTest" (fun () ->
     
         #if !FABLE_COMPILER
@@ -270,7 +270,7 @@ let curry = testList "Curry" [
         ())
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "uncurryTest" (fun () ->
         let g2  x y   = [x + y]
         let g3  x y z = [x + y + z]
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Alternative.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Alternative.fs
index aa5c35821..d1e72830c 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Alternative.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Alternative.fs
@@ -8,7 +8,7 @@ open FSharpPlus.Data
 
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 let testEmpty () =
     let _: WrappedListE<int> = empty
     let _: list<int>         = empty
@@ -21,7 +21,7 @@ let testEmpty () =
     ()
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 let testAppend () =
     let _ = WrappedListE [1;2] <|> WrappedListE [3;4]
     let _ = [1;2] <|> [3;4]
@@ -35,7 +35,7 @@ let testAppend () =
     ()
 #endif
 let alternative = testList "Alternative" [
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "testEmptyAndAppendForCustomType" (fun () ->
         let u = WrappedListE [1;2]
         let v = WrappedListG [1;2]
@@ -61,7 +61,7 @@ let alternative = testList "Alternative" [
         Assert.AreEqual (Some 1, z))
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "testChoice" (fun () ->
         let s = seq { 
             yield (SideEffects.add "a"; None)
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Applicative.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Applicative.fs
index 996e3a337..807cde466 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Applicative.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Applicative.fs
@@ -70,7 +70,7 @@ let applicative = testList "Applicative" [
         Assert.IsInstanceOf<Option<bool>> testGTE4)
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "applicatives" (fun () -> 
 
         let run (ZipList x) = x
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Collections.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Collections.fs
index c3b89ca3a..03aa88fb5 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Collections.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Collections.fs
@@ -14,7 +14,7 @@ module Collections =
 
     open System.Collections.Concurrent
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     let testCollections =
         let bigSeq = seq {1..10000000}
         let bigLst = [ 1..10000000 ]
@@ -39,7 +39,7 @@ module Collections =
         ()
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     let testSeqConversions =
         #if !FABLE_COMPILER
         let sk: Generic.Stack<_>          = ofSeq { 1 .. 3 }
@@ -125,7 +125,7 @@ module Collections =
         ()
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     let testListConversions =
 
         // From sequence
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Foldable.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Foldable.fs
index 1cfb152ab..c8a13450b 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Foldable.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Foldable.fs
@@ -9,7 +9,7 @@ open FSharpPlus.Data
 open System
 open System.Collections.ObjectModel
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 let foldables =
     let _10  = foldBack (+) (seq [1;2;3;4]) 0
     let _323 = toList (seq [3;2;3])
@@ -34,7 +34,7 @@ let foldable = testList "Foldable" [
         SideEffects.are [])
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "filterDefaultCustom" [
         #if !FABLE_COMPILER
         testCase "WrappedListA" (fun () ->
@@ -57,7 +57,7 @@ let foldable = testList "Foldable" [
     ]
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "foldAternatives" [
         testCase "Option list" (fun () ->
             let x = choice [None; Some 3; Some 4; None]
@@ -70,7 +70,7 @@ let foldable = testList "Foldable" [
     ]
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "fromToSeq" [
         #if !FABLE_COMPILER
         testCase "dictionary" (fun () ->
@@ -120,13 +120,13 @@ let foldable = testList "Foldable" [
         Assert.IsInstanceOf<Option<seq<int>>> (Some sortedSeq))
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "intersperse" (fun () ->
         equal "a,b,c,d,e" (intersperse ',' "abcde")
         equal ["a";",";"b";",";"c";",";"d";",";"e"] (intersperse "," ["a";"b";"c";"d";"e"]))
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "intercalate" (fun () ->
         equal "Lorem, ipsum, dolor" (intercalate ", " ["Lorem"; "ipsum"; "dolor"]))
 #endif
@@ -163,7 +163,7 @@ let foldable = testList "Foldable" [
         equal 50 (foldMap ((+) 10) iReadOnlyList))
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "exists" (fun () ->
         SideEffects.reset ()
         let _ = exists ((=) 2) [1..3]
@@ -175,7 +175,7 @@ let foldable = testList "Foldable" [
         ())
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "pick" [
         #if !FABLE_COMPILER
         testCase "StringBuilder" (fun () ->
@@ -201,7 +201,7 @@ let foldable = testList "Foldable" [
     ]
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "minimum" [
         testCase "list" (fun () ->
             let _ = minimum [1..3]
@@ -225,7 +225,7 @@ let foldable = testList "Foldable" [
     ]
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "maxBy" [
         testCase "list" (fun () ->
             let _ = maxBy id [1..3]
@@ -249,7 +249,7 @@ let foldable = testList "Foldable" [
     ]
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "length" [
         testCase "list" (fun () ->
             let _ = length [1..3]
@@ -273,7 +273,7 @@ let foldable = testList "Foldable" [
     ]
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "tryHead" [
         testCase "seq" (fun () ->
             let s                = tryHead <| seq [1;2]
@@ -306,7 +306,7 @@ let foldable = testList "Foldable" [
     ]
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "tryLast" (fun () ->
         let s                = tryLast <| seq [1;2]
         let s': int option   = tryLast <| seq []
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Functor.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Functor.fs
index 0a8a58e14..60d20a4fd 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Functor.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Functor.fs
@@ -34,7 +34,7 @@ let functor = testList "Functor" [
         let tenEncoded = StringCodec.encode intCodec 10
         equal oneParsed (Result<int, string>.Ok 1)
         equal tenEncoded "10" )
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "mapDefaultCustom" [
         testCase "nelist" (fun () -> 
 
@@ -140,7 +140,7 @@ let functor = testList "Functor" [
     ]
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "unzip" (fun () -> 
         let testVal = unzip {Head = (1, 'a'); Tail = [(2, 'b');(3, 'b')]}
         #if !FABLE_COMPILER
@@ -154,7 +154,7 @@ let functor = testList "Functor" [
         Assert.AreEqual((NonEmptyMap.Create((1,(true)), (2, (false))),NonEmptyMap.Create((1,('a')), (2, ( 'b')))),testVal2))
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "zipTest" (fun () ->
 
         SideEffects.reset ()
@@ -239,7 +239,7 @@ let functor = testList "Functor" [
         ())
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "genericZipShortest" (fun () ->
         let a = zip [|1; 2; 3|]  [|"a"; "b"|]
         equalSeq [|1,"a"; 2,"b"|] a
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Indexable.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Indexable.fs
index f9b439402..68c9fdd5d 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Indexable.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Indexable.fs
@@ -11,7 +11,7 @@ open System.Collections.ObjectModel
 open FSharpPlus.Control
 
 let indexable = testList "Indexable" [
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "testCompileAndExecuteItem" [
         testCase "map" (fun () ->
             let a = Map.ofSeq [1, "one"; 2, "two"]
@@ -68,7 +68,7 @@ let indexable = testList "Indexable" [
     ]
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "testCompileAndExecuteTryItem" [
         testCase "map" (fun () ->
             let a = Map.ofSeq [1, "one"; 2, "two"]
@@ -228,7 +228,7 @@ let indexable = testList "Indexable" [
         equalSeq ["Using WrappedMapA's TraverseIndexed"] (SideEffects.get ()))
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "findIndexUsage" (fun () ->
         let m1 = WrappedListD [0..4]
         SideEffects.reset ()
@@ -237,7 +237,7 @@ let indexable = testList "Indexable" [
         equal i1 2)
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "findSliceIndexUsage" (fun () ->
         let m1 = WrappedListD [0..4]
         let m2 = WrappedListD [1..3]
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Lensing.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Lensing.fs
index 41a32ee03..2f035d353 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Lensing.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Lensing.fs
@@ -5,7 +5,7 @@ open Testing
 open FSharpPlus
 open FSharpPlus.Data
 open System
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 open FSharpPlus.Lens
 type Person = { Name: string; DateOfBirth: DateTime }
 module Person =
@@ -20,7 +20,7 @@ let rayuela =
                  DateOfBirth = DateTime (1914, 8, 26) } }
 #endif
 let lensing = testList "Lensing" [
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "Lens" (fun () ->
                equal (view Book._authorName rayuela) "Julio Cortázar")
     testCase "Lens view 1, 2" (fun () ->
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Monad.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Monad.fs
index 6c4d17296..3d5c5ec33 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Monad.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Monad.fs
@@ -5,13 +5,13 @@ open FSharpPlus
 open FSharpPlus.Data
 #nowarn "686"
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 let option<'t> = monad<Option<'t>>
 let list<'t>   = monad'<list<'t>>
 #endif
 
 let monad = testList "Monad" [
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "joinDefaultCustom" (fun () -> 
         let x = join [[1];[2]]
         equal [1;2] x
@@ -23,7 +23,7 @@ let monad = testList "Monad" [
         equal ["Join"] (SideEffects.get ()))
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "workFlow" (fun () ->       
         let testVal = 
             monad {
@@ -43,17 +43,18 @@ let monad = testList "Monad" [
         equal None (cf |> Const.run |> First.run)
     )
     #endif
-    
+    #if !FABLE_COMPILER_4
     testCase "return Const First using explicit method" (fun () ->
         let cf : Const<First<int>,int> = Const.Return<_,_> 1
         equal None (cf |> Const.run |> First.run)
     )
+    #endif
     #if !FABLE_COMPILER
     testCase "return Const" (fun () ->
         let c : Const<int,int> = Control.Return.InvokeOnInstance 1 in equal 0 (Const.run c)
     )
     #endif
-    
+    #if !FABLE_COMPILER_4
     testCase "specialized maybe monad" (fun () ->
         let v = option {
             let! x = Some 10
@@ -71,6 +72,7 @@ let monad = testList "Monad" [
         }        
         equal [25] v
     )  
+    #endif
 
     //  Exception: RangeError: Maximum call stack size exceeded
     #if !FABLE_COMPILER
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Monoid.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Monoid.fs
index 4013c845d..b55907029 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Monoid.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Monoid.fs
@@ -10,7 +10,7 @@ open FSharpPlus.Data
 open System.Threading.Tasks
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 type ZipList<'s> = ZipList of 's seq with
     static member Return (x:'a)                               = ZipList (Seq.initInfinite (konst x))
     static member Map   (ZipList x, f: 'a->'b)                = ZipList (Seq.map f x)
@@ -44,7 +44,7 @@ let monoid = testList "Monoid" [
         #if !FABLE_COMPILER
         let (WrappedListB x) = Seq.sum [WrappedListB [10]; WrappedListB [15]]
         #endif
-        #if !FABLE_COMPILER || FABLE_COMPILER_3
+        #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
         //equalSeq [10;15] x // fails to infer type?
         let (WrappedListC y) = Seq.sum [WrappedListC [10]; WrappedListC [15]]
         equalSeq [10] y
@@ -71,7 +71,7 @@ let monoid = testList "Monoid" [
         equal ["Using optimized Sum"] (SideEffects.get ())
         #endif
 
-        #if !FABLE_COMPILER || FABLE_COMPILER_3
+        #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
         let _wl = WrappedListB  [2..10]
 
         let _arrayGroup = groupBy ((%)/> 2) [|11;2;3;9;5;6;7;8;9;10|]
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/MonoidCompile.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/MonoidCompile.fs
index c3cb17f2a..424b3c35e 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/MonoidCompile.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/MonoidCompile.fs
@@ -10,7 +10,7 @@ open FSharpPlus.Data
 open System.Threading.Tasks
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 type ZipList<'s> = ZipList of 's seq with
     static member Return (x:'a)                               = ZipList (Seq.initInfinite (konst x))
     static member Map   (ZipList x, f: 'a->'b)                = ZipList (Seq.map f x)
@@ -49,13 +49,13 @@ let testCompile =
     let _quot23      = plus       (zero)         <@ ResizeArray ([2;3])   @>
     let _quot13      = plus       (zero)         <@ ("1","3") @>
     #endif
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     let lzy1 = plus (lazy [1]) (lazy [2;3])
     #endif
     #if !FABLE_COMPILER
     let _lzy = plus (zero) lzy1
     #endif
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     let asy1 = plus (async.Return [1]) (async.Return [2;3])
     #endif
     #if !FABLE_COMPILER
@@ -64,7 +64,7 @@ let testCompile =
     let _bigNestedTuple2 = (1, System.Tuple (8, "ff",3,4,5,6,7,8,9,10,11,12,(),14,15,16,17,18,19,20)) ++ (zero, System.Tuple (8, "ff",3,4,5,6,7,8,9,10,11,12,(),14,15,16,17,18,19,20)) ++ zero
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     let _nes : NonEmptySeq<_> = plus (NonEmptySeq.singleton 1) (NonEmptySeq.singleton 2)
     #endif
 
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Numeric.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Numeric.fs
index a59077377..1f7fad674 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Numeric.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Numeric.fs
@@ -7,7 +7,7 @@ open System.Collections.Generic
 open FSharpPlus.Data
 
 let numeric = testList "Numeric" [
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "Zero First" (fun () -> let z : First<int> = getZero() in equal None (First.run z))
     #endif
     ]
\ No newline at end of file
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Parsing.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Parsing.fs
index 507a8190c..f9d545c73 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Parsing.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Parsing.fs
@@ -6,7 +6,7 @@ open FSharpPlus.Data
 #nowarn "686"
 open System
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 let (|Int32|_|) : _-> Int32 option = tryParse
 type ProductId = { Value:int }
 with
@@ -17,7 +17,7 @@ with
 #endif
 
 let parsing = testList "Parsing" [
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "parse" (fun () -> 
 
         let v2 : DateTimeOffset = parse "2011-03-04T15:42:19+03:00"
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Splits.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Splits.fs
index a6744faf5..fcddd4064 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Splits.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Splits.fs
@@ -17,7 +17,7 @@ type Sum<'a> = Sum of 'a with
 
 let splits = testList "Splits" [
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testCase "splitArraysAndStrings" (fun () ->
         let a1 = "this.isABa.tABCest"  |> split [|"AT" ; "ABC" |]
         let a2 = "this.isABa.tABCest"B |> split [|"AT"B; "ABC"B|]
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Traversable.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Traversable.fs
index a8dbe1dc7..5e5fc5b7c 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Traversable.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Traversable.fs
@@ -7,7 +7,7 @@ open FSharpPlus.Data
 open System.Threading.Tasks
 
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 type Either<'l,'r> = Left of 'l | Right of 'r with
     static member Return x = Right x
     static member inline get_Empty () = Left empty
@@ -26,7 +26,7 @@ let traverseTest =
 let toOptions x = if x <> 4 then Some x       else None
 let toChoices x = if x <> 4 then Choice1Of2 x else Choice2Of2 "This is a failure"
 let toLists   x = if x <> 4 then [x; x]       else []
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 let toEithers x = if x <> 4 then Right x else Left ["This is a failure"]
 #endif
 
@@ -85,7 +85,7 @@ let traversable = testList "Traversable" [
         ())
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "traverse_Order" [
         testCase "nelist" (fun () ->
             SideEffects.reset()
@@ -191,7 +191,7 @@ let traversable = testList "Traversable" [
         Assert.AreEqual (Either<string list,NonEmptySeq<int>>.Left ["This is a failure"], e))
     #endif
 
-    #if !FABLE_COMPILER || FABLE_COMPILER_3
+    #if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
     testList "traverseFiniteApplicatives" [ // TODO -> implement short-circuit without breaking anything else
 
         #if !FABLE_COMPILER
diff --git a/tests/FSharpPlusFable.Tests/FSharpTests/General/Util.fs b/tests/FSharpPlusFable.Tests/FSharpTests/General/Util.fs
index 95f499b84..a12f4f4ea 100644
--- a/tests/FSharpPlusFable.Tests/FSharpTests/General/Util.fs
+++ b/tests/FSharpPlusFable.Tests/FSharpTests/General/Util.fs
@@ -4,7 +4,7 @@ open FSharpPlus
 open FSharpPlus.Data
 open FSharpPlus.Control
 open Testing
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 type WrappedMapA<'K,'V when 'K : comparison> = WrappedMapA of Map<'K,'V> with
     static member ToMap (WrappedMapA m) = m
     static member inline TraverseIndexed (WrappedMapA m, f) =
@@ -42,7 +42,7 @@ type WrappedListA<'s> = WrappedListA of 's list with
         List.length lst
 #endif
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 type WrappedListB<'s> = WrappedListB of 's list with
     static member Return x = WrappedListB [x]
     static member (+) (WrappedListB l, WrappedListB x) = WrappedListB (l @ x)
@@ -63,7 +63,7 @@ type WrappedListC<'s> = WrappedListC of 's list with
     static member Zero = WrappedListC List.empty
     static member Sum (lst: seq<WrappedListC<_>>) = Seq.head lst
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 type WrappedListD<'s> = WrappedListD of 's list with
     interface Collections.Generic.IEnumerable<'s> with member x.GetEnumerator () = (let (WrappedListD x) = x in x :> _ seq).GetEnumerator ()
     interface Collections.IEnumerable             with member x.GetEnumerator () = (let (WrappedListD x) = x in x :> _ seq).GetEnumerator () :> Collections.IEnumerator
@@ -139,7 +139,7 @@ type WrappedListG<'s> = WrappedListG of 's list with
     static member Delay (f: unit -> WrappedListG<_>) = SideEffects.add "Using WrappedListG's Delay"; f ()
     static member Using (resource, body)             = SideEffects.add "Using WrappedListG's Using"; using resource body
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 type WrappedListH<'s> = WrappedListH of 's list with
     static member Map (WrappedListH lst, f) = WrappedListH (List.map f lst)
     static member inline Sequence (x: WrappedListH<'``Functor<'T>``>) =
@@ -200,7 +200,7 @@ type WrappedSeqC<'s> = WrappedSeqC of 's seq with
                     SideEffects.add "Using WrappedSeqC's TryFinally"
                     try computation finally compensation ()
 
-#if !FABLE_COMPILER || FABLE_COMPILER_3
+#if (!FABLE_COMPILER || FABLE_COMPILER_3) && !FABLE_COMPILER_4
 type WrappedSeqD<'s> = WrappedSeqD of 's seq with
     static member Return x = SideEffects.add "Using WrappedSeqD's Return"; WrappedSeqD (Seq.singleton x)
     static member (<*>)  (WrappedSeqD f, WrappedSeqD x) = SideEffects.add "Using WrappedSeqD's Apply"; WrappedSeqD (f <*> x)
diff --git a/tests/FSharpPlusFable.Tests/package.json b/tests/FSharpPlusFable.Tests/package.json
index a2531bd1d..4572c8daf 100644
--- a/tests/FSharpPlusFable.Tests/package.json
+++ b/tests/FSharpPlusFable.Tests/package.json
@@ -2,7 +2,7 @@
   "private": true,
   "type": "module",
   "scripts": {
-    "test": "dotnet fable . --outDir bin --runScript ./bin /d",
+    "test": "fable . --outDir bin --runScript ./bin /d",
     "test_debug": "node --eval \"require('esm')(module)('./bin/./Tests.js')\" ./bin/./Tests.js ./bin /d"
   },
   "name": "tests"