diff --git a/src/zarr/core/metadata/v3.py b/src/zarr/core/metadata/v3.py
index 6efc11ed44..147ab0b755 100644
--- a/src/zarr/core/metadata/v3.py
+++ b/src/zarr/core/metadata/v3.py
@@ -7,7 +7,7 @@
 from zarr.core.buffer.core import default_buffer_prototype
 
 if TYPE_CHECKING:
-    from typing import Self
+    from typing import Callable, Self
 
     from zarr.core.buffer import Buffer, BufferPrototype
     from zarr.core.chunk_grids import ChunkGrid
@@ -137,14 +137,14 @@ class V3JsonEncoder(json.JSONEncoder):
     def __init__(
         self,
         *,
-        skipkeys=False,
-        ensure_ascii=True,
-        check_circular=True,
-        allow_nan=True,
-        sort_keys=False,
-        indent=None,
-        separators=None,
-        default=None,
+        skipkeys: bool = False,
+        ensure_ascii: bool = True,
+        check_circular: bool = True,
+        allow_nan: bool = True,
+        sort_keys: bool = False,
+        indent: int | None = None,
+        separators: tuple[str, str] | None = None,
+        default: Callable | None = None,
     ) -> None:
         if indent is None:
             indent = config.get("json_indent")