diff --git a/airflow/providers/microsoft/azure/hooks/cosmos.py b/airflow/providers/microsoft/azure/hooks/cosmos.py
index 0da5cb2cc37ea..ed475978b0345 100644
--- a/airflow/providers/microsoft/azure/hooks/cosmos.py
+++ b/airflow/providers/microsoft/azure/hooks/cosmos.py
@@ -86,7 +86,7 @@ def get_ui_field_behaviour() -> Dict[str, Any]:
     def __init__(self, azure_cosmos_conn_id: str = default_conn_name) -> None:
         super().__init__()
         self.conn_id = azure_cosmos_conn_id
-        self._conn = None
+        self._conn: Optional[CosmosClient] = None
 
         self.default_database_name = None
         self.default_collection_name = None