diff --git a/src/Aws/Common/Client/AbstractClient.php b/src/Aws/Common/Client/AbstractClient.php
index 63a46832f7..d01b0f2e57 100644
--- a/src/Aws/Common/Client/AbstractClient.php
+++ b/src/Aws/Common/Client/AbstractClient.php
@@ -83,9 +83,7 @@ public function __construct(CredentialsInterface $credentials, SignatureInterfac
 
         // Add the event listener so that requests are signed before they are sent
         $dispatcher = $this->getEventDispatcher();
-        if (!$credentials instanceof NullCredentials) {
-            $dispatcher->addSubscriber(new SignatureListener($credentials, $signature));
-        }
+        $dispatcher->addSubscriber(new SignatureListener($credentials, $signature));
 
         if ($backoff = $config->get(Options::BACKOFF)) {
             $dispatcher->addSubscriber($backoff, -255);
diff --git a/src/Aws/Common/Signature/SignatureListener.php b/src/Aws/Common/Signature/SignatureListener.php
index d24d252000..e53f36718f 100644
--- a/src/Aws/Common/Signature/SignatureListener.php
+++ b/src/Aws/Common/Signature/SignatureListener.php
@@ -17,6 +17,7 @@
 namespace Aws\Common\Signature;
 
 use Aws\Common\Credentials\CredentialsInterface;
+use Aws\Common\Credentials\NullCredentials;
 use Guzzle\Common\Event;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
 
@@ -75,6 +76,8 @@ public function onCredentialsChanged(Event $event)
      */
     public function onRequestBeforeSend(Event $event)
     {
-        $this->signature->signRequest($event['request'], $this->credentials);
+        if(!$this->credentials instanceof NullCredentials) {
+            $this->signature->signRequest($event['request'], $this->credentials);
+        }
     }
 }
diff --git a/tests/Aws/Tests/Common/Client/AbstractClientTest.php b/tests/Aws/Tests/Common/Client/AbstractClientTest.php
index 584d168569..31885c2a0f 100644
--- a/tests/Aws/Tests/Common/Client/AbstractClientTest.php
+++ b/tests/Aws/Tests/Common/Client/AbstractClientTest.php
@@ -19,6 +19,7 @@
 use Aws\Common\Aws;
 use Aws\Common\Client\AbstractClient;
 use Aws\Common\Client\AwsClientInterface;
+use Aws\Common\Credentials\NullCredentials;
 use Aws\Common\Enum\Region;
 use Aws\Common\Signature\SignatureV4;
 use Aws\Common\Signature\SignatureListener;
@@ -47,12 +48,12 @@ public function testConstructorConfiguresClient()
         $this->assertSame($config, $client->getConfig());
 
         // Ensure a signature event dispatcher was added
-        $this->assertGreaterThan(0, array_filter(
+        $this->assertGreaterThan(0, count(array_filter(
             $client->getEventDispatcher()->getListeners('request.before_send'),
             function($e) {
                 return $e[0] instanceof SignatureListener;
             }
-        ));
+        )));
 
         // Ensure that the user agent string is correct
         $expectedUserAgent = 'aws-sdk-php2/' . Aws::VERSION;
@@ -60,6 +61,26 @@ function($e) {
         $this->assertRegExp("@^{$expectedUserAgent}@", $actualUserAgent);
     }
 
+    public function testConstructorAlwaysConfiguresSignatureListener()
+    {
+        $signature = new SignatureV4();
+        $credentials = new NullCredentials();
+        $config = new Collection();
+
+        $client = $this->getMockBuilder('Aws\Common\Client\AbstractClient')
+          ->setConstructorArgs(array($credentials, $signature, $config))
+          ->getMockForAbstractClass();
+
+        // Ensure a signature event dispatcher was added
+        $this->assertGreaterThan(0, count(array_filter(
+          $client->getEventDispatcher()->getListeners('request.before_send'),
+          function($e) {
+              return $e[0] instanceof SignatureListener;
+          }
+        )));
+
+    }
+
     public function testUsesDefaultWaiterFactory()
     {
         $client = $this->getMockBuilder('Aws\Common\Client\AbstractClient')
diff --git a/tests/Aws/Tests/Common/Signature/SignatureListenerTest.php b/tests/Aws/Tests/Common/Signature/SignatureListenerTest.php
index f00835c566..bb0bfa5f67 100644
--- a/tests/Aws/Tests/Common/Signature/SignatureListenerTest.php
+++ b/tests/Aws/Tests/Common/Signature/SignatureListenerTest.php
@@ -17,6 +17,7 @@
 namespace Aws\Tests\Common\Signature;
 
 use Aws\Common\Credentials\Credentials;
+use Aws\Common\Credentials\NullCredentials;
 use Aws\Common\Signature\SignatureListener;
 use Guzzle\Common\Collection;
 use Guzzle\Http\Message\Request;
@@ -49,6 +50,26 @@ public function testSignsRequestsProperly()
         $listener->onRequestBeforeSend($event);
     }
 
+    public function testDoesNotSignNullCredentialRequests() {
+        $request = new Request('GET', 'http://www.example.com');
+        $request->getEventDispatcher();
+        $credentials = new NullCredentials();
+        $signature = $this->getMock('Aws\Common\Signature\SignatureV4');
+
+        // Ensure that signing the request occurred once with the correct args
+        $signature->expects($this->never())
+          ->method('signRequest');
+
+        $listener = new SignatureListener($credentials, $signature);
+
+        // Create a mock event
+        $event = new Event(array(
+          'request' => $request
+        ));
+
+        $listener->onRequestBeforeSend($event);
+    }
+
     public function testCredentialsGetUpdated()
     {
         $credentials = new Credentials('access-key-one', 'secret');