diff --git a/src/python/grpcio/grpc/aio/_call.py b/src/python/grpcio/grpc/aio/_call.py
index ef3a624bec4..5a414c8e3e1 100644
--- a/src/python/grpcio/grpc/aio/_call.py
+++ b/src/python/grpcio/grpc/aio/_call.py
@@ -165,7 +165,7 @@ class Call:
     _loop: asyncio.AbstractEventLoop
     _code: grpc.StatusCode
     _cython_call: cygrpc._AioCall
-    _metadata: Tuple[MetadatumType]
+    _metadata: Tuple[MetadatumType, ...]
     _request_serializer: SerializingFunction
     _response_deserializer: DeserializingFunction