diff --git a/gcloud/_testing.py b/gcloud/_testing.py
index 0a440e817436..15ef5dd298e1 100644
--- a/gcloud/_testing.py
+++ b/gcloud/_testing.py
@@ -59,3 +59,17 @@ def __init__(self, items, page_token):
     def next(self):
         items, self._items = self._items, None
         return items
+
+
+class _GAXBundlingEvent(object):
+
+    result = None
+
+    def __init__(self, result):
+        self._result = result
+
+    def is_set(self):
+        return self.result is not None
+
+    def wait(self, *_):
+        self.result = self._result
diff --git a/gcloud/pubsub/_gax.py b/gcloud/pubsub/_gax.py
index 28ac6c23e294..0639833feb73 100644
--- a/gcloud/pubsub/_gax.py
+++ b/gcloud/pubsub/_gax.py
@@ -162,17 +162,17 @@ def topic_publish(self, topic_path, messages):
         :raises: :exc:`gcloud.exceptions.NotFound` if the topic does not
                     exist
         """
-        options = CallOptions(is_bundling=False)
         message_pbs = [_message_pb_from_dict(message)
                        for message in messages]
         try:
-            result = self._gax_api.publish(topic_path, message_pbs,
-                                           options=options)
+            event = self._gax_api.publish(topic_path, message_pbs)
+            if not event.is_set():
+                event.wait()
         except GaxError as exc:
             if exc_to_code(exc.cause) == StatusCode.NOT_FOUND:
                 raise NotFound(topic_path)
             raise
-        return result.message_ids
+        return event.result.message_ids
 
     def topic_list_subscriptions(self, topic_path, page_size=0,
                                  page_token=None):
diff --git a/gcloud/pubsub/test__gax.py b/gcloud/pubsub/test__gax.py
index 2426d2dfb7e8..d285cb6e3260 100644
--- a/gcloud/pubsub/test__gax.py
+++ b/gcloud/pubsub/test__gax.py
@@ -204,12 +204,15 @@ def test_topic_delete_error(self):
 
     def test_topic_publish_hit(self):
         import base64
+        from gcloud._testing import _GAXBundlingEvent
         PAYLOAD = b'This is the message text'
         B64 = base64.b64encode(PAYLOAD).decode('ascii')
         MSGID = 'DEADBEEF'
         MESSAGE = {'data': B64, 'attributes': {}}
         response = _PublishResponsePB([MSGID])
-        gax_api = _GAXPublisherAPI(_publish_response=response)
+        event = _GAXBundlingEvent(response)
+        event.wait()  # already received result
+        gax_api = _GAXPublisherAPI(_publish_response=event)
         api = self._makeOne(gax_api)
 
         resource = api.topic_publish(self.TOPIC_PATH, [MESSAGE])
@@ -220,7 +223,29 @@ def test_topic_publish_hit(self):
         message_pb, = message_pbs
         self.assertEqual(message_pb.data, B64)
         self.assertEqual(message_pb.attributes, {})
-        self.assertEqual(options.is_bundling, False)
+        self.assertEqual(options, None)
+
+    def test_topic_publish_hit_with_wait(self):
+        import base64
+        from gcloud._testing import _GAXBundlingEvent
+        PAYLOAD = b'This is the message text'
+        B64 = base64.b64encode(PAYLOAD).decode('ascii')
+        MSGID = 'DEADBEEF'
+        MESSAGE = {'data': B64, 'attributes': {}}
+        response = _PublishResponsePB([MSGID])
+        event = _GAXBundlingEvent(response)
+        gax_api = _GAXPublisherAPI(_publish_response=event)
+        api = self._makeOne(gax_api)
+
+        resource = api.topic_publish(self.TOPIC_PATH, [MESSAGE])
+
+        self.assertEqual(resource, [MSGID])
+        topic_path, message_pbs, options = gax_api._publish_called_with
+        self.assertEqual(topic_path, self.TOPIC_PATH)
+        message_pb, = message_pbs
+        self.assertEqual(message_pb.data, B64)
+        self.assertEqual(message_pb.attributes, {})
+        self.assertEqual(options, None)
 
     def test_topic_publish_miss_w_attrs_w_bytes_payload(self):
         import base64
@@ -239,7 +264,7 @@ def test_topic_publish_miss_w_attrs_w_bytes_payload(self):
         message_pb, = message_pbs
         self.assertEqual(message_pb.data, B64)
         self.assertEqual(message_pb.attributes, {'foo': 'bar'})
-        self.assertEqual(options.is_bundling, False)
+        self.assertEqual(options, None)
 
     def test_topic_publish_error(self):
         import base64
@@ -258,7 +283,7 @@ def test_topic_publish_error(self):
         message_pb, = message_pbs
         self.assertEqual(message_pb.data, B64)
         self.assertEqual(message_pb.attributes, {})
-        self.assertEqual(options.is_bundling, False)
+        self.assertEqual(options, None)
 
     def test_topic_list_subscriptions_no_paging(self):
         from google.gax import INITIAL_PAGE