diff --git a/lib/Constant.ml b/lib/Constant.ml
index 7dbe7ec4..89ff139a 100644
--- a/lib/Constant.ml
+++ b/lib/Constant.ml
@@ -28,6 +28,7 @@ let bytes_of_width (w: width) =
 type op =
   (* Arithmetic operations *)
   | Add | AddW | Sub | SubW | Div | DivW | Mult | MultW | Mod
+  | Neg
   (* Bitwise operations *)
   | BOr | BAnd | BXor | BShiftL | BShiftR | BNot
   (* Arithmetic comparisons / boolean comparisons *)
diff --git a/lib/Helpers.ml b/lib/Helpers.ml
index 969f803b..8e14d561 100644
--- a/lib/Helpers.ml
+++ b/lib/Helpers.ml
@@ -45,7 +45,7 @@ let type_of_op op w =
       TArrow (TBool, TArrow (TBool, TBool))
   | Not ->
       TArrow (TBool, TBool)
-  | BNot ->
+  | BNot | Neg ->
       TArrow (TInt w, TInt w)
   | Assign | PreIncr | PreDecr | PostIncr | PostDecr | Comma ->
       invalid_arg "type_of_op"
diff --git a/lib/PrintC.ml b/lib/PrintC.ml
index 018a79f6..905c7752 100644
--- a/lib/PrintC.ml
+++ b/lib/PrintC.ml
@@ -129,7 +129,7 @@ and p_type_name (qs, spec, decl) =
   | _ ->
       p_qualifiers_break qs ^^ p_type_spec spec ^^ space ^^ p_type_declarator decl
 
-(* http:/ /en.cppreference.com/w/c/language/operator_precedence *)
+(* http://en.cppreference.com/w/c/language/operator_precedence *)
 and prec_of_op2 op =
   let open Constant in
   match op with
@@ -151,12 +151,12 @@ and prec_of_op2 op =
   | Or -> 12, 12, 12
   | Assign -> 14, 13, 14
   | Comma -> 15, 15, 14
-  | PreIncr | PostIncr | PreDecr | PostDecr | Not | BNot -> raise (Invalid_argument "prec_of_op2")
+  | PreIncr | PostIncr | PreDecr | PostDecr | Not | BNot | Neg -> raise (Invalid_argument "prec_of_op2")
 
 and prec_of_op1 op =
   let open Constant in
   match op with
-  | PreDecr | PreIncr | Not | BNot -> 2
+  | PreDecr | PreIncr | Not | BNot | Neg -> 2
   | PostDecr | PostIncr -> 1
   | _ -> raise (Invalid_argument "prec_of_op1")
 
diff --git a/lib/PrintCommon.ml b/lib/PrintCommon.ml
index 41b3b6fb..2951a1a3 100644
--- a/lib/PrintCommon.ml
+++ b/lib/PrintCommon.ml
@@ -69,6 +69,7 @@ let print_op = function
   | PostDecr | PreDecr -> string "--"
   | Assign -> string "="
   | Comma -> string ","
+  | Neg -> string "-"
 
 let print_cc = function
   | CDecl -> string "__cdecl"