diff --git a/google/cloud/ndb/client.py b/google/cloud/ndb/client.py
index fa9ad890..3323a96f 100644
--- a/google/cloud/ndb/client.py
+++ b/google/cloud/ndb/client.py
@@ -15,6 +15,7 @@
 """A client for NDB which manages credentials, project, namespace."""
 
 import contextlib
+import gc
 import grpc
 import os
 import requests
@@ -200,6 +201,11 @@ def context(
             # Finish up any work left to do on the event loop
             context.eventloop.run()
 
+        # Work around bug where thread started by `google.auth` angers the
+        # Google App Engine Python 2.7 Runtime. See issue #336.
+        # https://github.com/googleapis/python-ndb/issues/336
+        gc.collect()
+
     @property
     def _http(self):
         """Getter for object used for HTTP transport.