diff --git a/pubsub/google/cloud/pubsub/subscription.py b/pubsub/google/cloud/pubsub/subscription.py
index c98277d660df..e76abcf94dd8 100644
--- a/pubsub/google/cloud/pubsub/subscription.py
+++ b/pubsub/google/cloud/pubsub/subscription.py
@@ -509,4 +509,5 @@ def __enter__(self):
         return self
 
     def __exit__(self, exc_type, exc_val, exc_tb):
-        self._subscription.acknowledge(list(self), self._client)
+        if self:
+            self._subscription.acknowledge(list(self), self._client)
diff --git a/pubsub/unit_tests/test_subscription.py b/pubsub/unit_tests/test_subscription.py
index 6d4dc1068f2a..6078a3cc70c8 100644
--- a/pubsub/unit_tests/test_subscription.py
+++ b/pubsub/unit_tests/test_subscription.py
@@ -14,6 +14,8 @@
 
 import unittest
 
+import mock
+
 
 class TestSubscription(unittest.TestCase):
     PROJECT = 'PROJECT'
@@ -745,6 +747,16 @@ def test___exit___(self):
                          [ACK_ID1, ACK_ID2])
         self.assertIs(subscription._ack_client, CLIENT)
 
+    def test_empty_ack_no_acknowledge(self):
+        subscription = mock.Mock(_FauxSubscription)
+        subscription.pull = lambda *args: []
+
+        auto_ack = self._make_one(subscription)
+        with auto_ack:
+            pass
+
+        subscription.acknowledge.assert_not_called()
+
 
 class _FauxIAMPolicy(object):