diff --git a/src/python/grpcio_test/grpc_test/framework/interfaces/face/_blocking_invocation_inline_service.py b/src/python/grpcio_test/grpc_test/framework/interfaces/face/_blocking_invocation_inline_service.py
index 8804f3f223325e1746c910793d4d8b7259ed88d2..b7dd5d4d17199a8f93d121ff152ee926ffa12927 100644
--- a/src/python/grpcio_test/grpc_test/framework/interfaces/face/_blocking_invocation_inline_service.py
+++ b/src/python/grpcio_test/grpc_test/framework/interfaces/face/_blocking_invocation_inline_service.py
@@ -73,6 +73,7 @@ class TestCase(test_coverage.Coverage, unittest.TestCase):
 
     Overriding implementations must call this implementation.
     """
+    self._invoker = None
     self.implementation.destantiate(self._memo)
 
   def testSuccessfulUnaryRequestUnaryResponse(self):
diff --git a/src/python/grpcio_test/grpc_test/framework/interfaces/face/_event_invocation_synchronous_event_service.py b/src/python/grpcio_test/grpc_test/framework/interfaces/face/_event_invocation_synchronous_event_service.py
index 5a78b4bed2486848fb4272a6ffc3d35a2fdc0e43..7cb273bf7873314d0fde090805e01087d60a55cc 100644
--- a/src/python/grpcio_test/grpc_test/framework/interfaces/face/_event_invocation_synchronous_event_service.py
+++ b/src/python/grpcio_test/grpc_test/framework/interfaces/face/_event_invocation_synchronous_event_service.py
@@ -74,6 +74,7 @@ class TestCase(test_coverage.Coverage, unittest.TestCase):
 
     Overriding implementations must call this implementation.
     """
+    self._invoker = None
     self.implementation.destantiate(self._memo)
 
   def testSuccessfulUnaryRequestUnaryResponse(self):
diff --git a/src/python/grpcio_test/grpc_test/framework/interfaces/face/_future_invocation_asynchronous_event_service.py b/src/python/grpcio_test/grpc_test/framework/interfaces/face/_future_invocation_asynchronous_event_service.py
index d1107e1576d793d4b63e89999249f97fece55d12..272a37f15f818c7cf81788eece97ec836fa0caf6 100644
--- a/src/python/grpcio_test/grpc_test/framework/interfaces/face/_future_invocation_asynchronous_event_service.py
+++ b/src/python/grpcio_test/grpc_test/framework/interfaces/face/_future_invocation_asynchronous_event_service.py
@@ -103,6 +103,7 @@ class TestCase(test_coverage.Coverage, unittest.TestCase):
 
     Overriding implementations must call this implementation.
     """
+    self._invoker = None
     self.implementation.destantiate(self._memo)
     self._digest_pool.shutdown(wait=True)