diff --git a/src/python/grpcio_tests/tests_py3_only/unit/_simple_stubs_test.py b/src/python/grpcio_tests/tests_py3_only/unit/_simple_stubs_test.py
index f7a80081fce..dc6a047f641 100644
--- a/src/python/grpcio_tests/tests_py3_only/unit/_simple_stubs_test.py
+++ b/src/python/grpcio_tests/tests_py3_only/unit/_simple_stubs_test.py
@@ -337,7 +337,7 @@ class SimpleStubsTest(unittest.TestCase):
                                   grpc.ChannelConnectivity.CONNECTING):
                 pass
             else:
-                raise AssertionError("Encountered unknown state.")
+                self.fail("Encountered unknown state.")
 
         channel.subscribe(_on_connectivity_changed)