Fix issues with App Engine datastore
diff --git a/tests/test_oauth2client.py b/tests/test_oauth2client.py
index 14beb97..4063e8b 100644
--- a/tests/test_oauth2client.py
+++ b/tests/test_oauth2client.py
@@ -101,6 +101,9 @@
     json = self.credentials.to_json()
     instance = OAuth2Credentials.from_json(json)
     self.assertEquals(type(instance), OAuth2Credentials)
+    instance.token_expiry = None
+    self.credentials.token_expiry = None
+
     self.assertEquals(self.credentials.__dict__, instance.__dict__)