diff --git a/src/zarr/core/metadata/v2.py b/src/zarr/core/metadata/v2.py
index 27c1badaf..4a9baaf8b 100644
--- a/src/zarr/core/metadata/v2.py
+++ b/src/zarr/core/metadata/v2.py
@@ -52,7 +52,7 @@ def __init__(
         compressor: numcodecs.abc.Codec | dict[str, JSON] | None = None,
         filters: Iterable[numcodecs.abc.Codec | dict[str, JSON]] | None = None,
         attributes: dict[str, JSON] | None = None,
-    ):
+    ) -> None:
         """
         Metadata for a Zarr version 2 array.
         """
diff --git a/src/zarr/core/metadata/v3.py b/src/zarr/core/metadata/v3.py
index f1cb07fd4..16bfc822a 100644
--- a/src/zarr/core/metadata/v3.py
+++ b/src/zarr/core/metadata/v3.py
@@ -72,7 +72,7 @@ def parse_dimension_names(data: object) -> tuple[str | None, ...] | None:
 
 
 class V3JsonEncoder(json.JSONEncoder):
-    def __init__(self, *args: Any, **kwargs: Any):
+    def __init__(self, *args: Any, **kwargs: Any) -> None:
         self.indent = kwargs.pop("indent", config.get("json_indent"))
         super().__init__(*args, **kwargs)
 
diff --git a/src/zarr/store/zip.py b/src/zarr/store/zip.py
index 2c3b16a65..cd9df4d37 100644
--- a/src/zarr/store/zip.py
+++ b/src/zarr/store/zip.py
@@ -56,7 +56,7 @@ def __init__(
         mode: ZipStoreAccessModeLiteral = "r",
         compression: int = zipfile.ZIP_STORED,
         allowZip64: bool = True,
-    ):
+    ) -> None:
         super().__init__(mode=mode)
 
         if isinstance(path, str):