diff --git a/lib/pubsub/subscription.js b/lib/pubsub/subscription.js
index 006b3cdbed7..82a2babcd1f 100644
--- a/lib/pubsub/subscription.js
+++ b/lib/pubsub/subscription.js
@@ -360,7 +360,7 @@ Subscription.prototype.pull = function(options, callback) {
     var messages = response.receivedMessages || [];
     messages = messages.map(Subscription.formatMessage_);
 
-    if (self.autoAck) {
+    if (self.autoAck && messages.length !== 0) {
       var ackIds = messages.map(function(message) {
         return message.ackId;
       });
diff --git a/test/pubsub/subscription.js b/test/pubsub/subscription.js
index 2be34b0782a..cb403c6c137 100644
--- a/test/pubsub/subscription.js
+++ b/test/pubsub/subscription.js
@@ -285,6 +285,18 @@ describe('Subscription', function() {
         subscription.pull({}, assert.ifError);
       });
 
+      it('should not autoAck if no messages returned', function(done) {
+        subscription.makeReq_ = function(method, path, qs, body, callback) {
+          callback(null, { receivedMessages: [] });
+        };
+        subscription.ack = function() {
+          throw new Error('I should not run.');
+        };
+        subscription.pull(function() {
+          done();
+        });
+      });
+
       it('should pass id to ack', function(done) {
         subscription.ack = function(id) {
           assert.equal(id, expectedMessage.ackId);