diff --git a/stream_chat/base/client.py b/stream_chat/base/client.py
index 6fd0eaf..dd3d3aa 100644
--- a/stream_chat/base/client.py
+++ b/stream_chat/base/client.py
@@ -73,7 +73,11 @@ def normalize_sort(self, sort: Union[Dict, List[Dict]] = None) -> List[Dict]:
         return sort_fields
 
     def create_token(
-        self, user_id: str, exp: int = None, iat: int = None, **claims: Any
+        self,
+        user_id: str,
+        exp: Optional[int] = None,
+        iat: Optional[int] = None,
+        **claims: Any,
     ) -> str:
         """
         Creates a JWT for a user.