diff --git a/supabase_functions/__init__.py b/supabase_functions/__init__.py
index 5c99910..9bb74e6 100644
--- a/supabase_functions/__init__.py
+++ b/supabase_functions/__init__.py
@@ -1,6 +1,6 @@
 from __future__ import annotations
 
-from typing import Literal, Union, overload
+from typing import Literal, Optional, Union, overload
 
 from ._async.functions_client import AsyncFunctionsClient
 from ._sync.functions_client import SyncFunctionsClient
diff --git a/supabase_functions/_async/functions_client.py b/supabase_functions/_async/functions_client.py
index 9705774..4a037f9 100644
--- a/supabase_functions/_async/functions_client.py
+++ b/supabase_functions/_async/functions_client.py
@@ -35,7 +35,7 @@ async def _request(
         self,
         method: Literal["GET", "OPTIONS", "HEAD", "POST", "PUT", "PATCH", "DELETE"],
         url: str,
-        headers: Union[Dict[str, str], None] = None,
+        headers: Optional[Dict[str, str]] = None,
         json: Optional[Dict[Any, Any]] = None,
     ) -> Response:
         response = await self._client.request(method, url, json=json, headers=headers)
diff --git a/supabase_functions/_sync/functions_client.py b/supabase_functions/_sync/functions_client.py
index 372d864..3550219 100644
--- a/supabase_functions/_sync/functions_client.py
+++ b/supabase_functions/_sync/functions_client.py
@@ -35,7 +35,7 @@ def _request(
         self,
         method: Literal["GET", "OPTIONS", "HEAD", "POST", "PUT", "PATCH", "DELETE"],
         url: str,
-        headers: Union[Dict[str, str], None] = None,
+        headers: Optional[Dict[str, str]] = None,
         json: Optional[Dict[Any, Any]] = None,
     ) -> Response:
         response = self._client.request(method, url, json=json, headers=headers)