diff --git a/python/minimal_test.py b/python/minimal_test.py
index 14362b6..353b4d2 100644
--- a/python/minimal_test.py
+++ b/python/minimal_test.py
@@ -166,6 +166,15 @@
       count += 1
     self.assertEqual(count, 3)
     self.assertEqual(len(expected), 0)
+  
+  def testIsInitializedStub(self):
+    proto = unittest_pb2.TestRequiredForeign()
+    self.assertTrue(proto.IsInitialized())
+    self.assertFalse(proto.optional_message.IsInitialized())
+    errors = []
+    self.assertFalse(proto.optional_message.IsInitialized(errors))
+    self.assertEqual(['a', 'b', 'c'], errors)
+    self.assertRaises(message.EncodeError, proto.optional_message.SerializeToString)
 
 if __name__ == '__main__':
     unittest.main(verbosity=2)