diff --git a/src/python/grpcio_tests/tests/tests.json b/src/python/grpcio_tests/tests/tests.json
index 678ce03093e..eb702f6c8b0 100644
--- a/src/python/grpcio_tests/tests/tests.json
+++ b/src/python/grpcio_tests/tests/tests.json
@@ -70,7 +70,6 @@
   "unit._server_test.ServerTest",
   "unit._server_wait_for_termination_test.ServerWaitForTerminationTest",
   "unit._session_cache_test.SSLSessionCacheTest",
-  "unit.py3_only._simple_stubs_test.SimpleStubsTest",
   "unit._signal_handling_test.SignalHandlingTest",
   "unit._version_test.VersionTest",
   "unit.beta._beta_features_test.BetaFeaturesTest",
diff --git a/src/python/grpcio_tests/tests/unit/py3_only/_simple_stubs_test.py b/src/python/grpcio_tests/tests/unit/py3_only/_simple_stubs_test.py
index abe48c92351..61a9117400c 100644
--- a/src/python/grpcio_tests/tests/unit/py3_only/_simple_stubs_test.py
+++ b/src/python/grpcio_tests/tests/unit/py3_only/_simple_stubs_test.py
@@ -13,6 +13,8 @@
 # limitations under the License.
 """Tests for Simple Stubs."""
 
+# TODO(https://github.com/grpc/grpc/issues/21965): Run under setuptools.
+
 import os
 
 _MAXIMUM_CHANNELS = 10