diff --git a/.travis.yml b/.travis.yml
index 6c322ae..5a4f48c 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -4,7 +4,6 @@ php:
   - 5.6
   - 5.5
   - 5.4
-  - 5.3
   - hhvm
 
 install: composer install
diff --git a/README.md b/README.md
index 84e165c..733b49f 100644
--- a/README.md
+++ b/README.md
@@ -1,18 +1,19 @@
-HTTP Signatures Guzzle 3
+HTTP Signatures Guzzle 4
 ===
 
-[![Build Status](https://travis-ci.org/99designs/http-signatures-guzzle.svg)](https://travis-ci.org/99designs/http-signatures-guzzle)
+[![Build Status](https://travis-ci.org/99designs/http-signatures-guzzlehttp.svg)](https://travis-ci.org/99designs/http-signatures-guzzlehttp)
 
-Adds Guzzle 3 support to [99designs/http-signatures][99signatures]
+Adds [99designs/http-signatures](http-signatures) support to Guzzle 4.  
+For Guzzle 3 see the [99designs/http-signatures-guzzle](99designs/http-signatures-guzzle) repo.
 
-Signing with Guzzle 3
+Signing with Guzzle 4
 ---
 
 This library includes support for automatically signing Guzzle requests using an event subscriber.
 
 ```php
 use HttpSignatures\Context;
-use HttpSignatures\Guzzle\RequestSubscriber;
+use HttpSignatures\GuzzleHttp\RequestSubscriber;
 
 $context = new Context(array(
   'keys' => array('examplekey' => 'secret-key-here'),
@@ -21,17 +22,15 @@ $context = new Context(array(
 ));
 
 $client = new \Guzzle\Http\Client('http://example.org');
-$client->addSubscriber(new RequestSubscriber($context));
+$client->getEmiter()->attach(new RequestSubscriber($context));
 
 // The below will now send a signed request to: http://example.org/path?query=123
 $client->get('/path?query=123', array(
   'Date' => 'Wed, 30 Jul 2014 16:40:19 -0700',
   'Accept' => 'llamas',
-))->send();
+));
 ```
 
 ## Contributing
 
 Pull Requests are welcome.
-
-[99signatures]: https://github.com/99designs/http-signatures-php
diff --git a/composer.json b/composer.json
index 6a6cd50..ff25532 100644
--- a/composer.json
+++ b/composer.json
@@ -1,13 +1,17 @@
 {
-    "name": "99designs/http-signatures-guzzle",
-    "description": "Sign and verify HTTP messages with Guzzle",
-    "homepage": "https://github.com/99designs/http-signatures-guzzle",
-    "keywords": ["http", "https", "signing", "signed", "signature", "hmac", "guzzle"],
+    "name": "99designs/http-signatures-guzzlehttp",
+    "description": "Sign and verify HTTP messages with Guzzle 4",
+    "homepage": "https://github.com/99designs/http-signatures-guzzlehttp",
+    "keywords": ["http", "https", "signing", "signed", "signature", "hmac", "guzzle 4"],
     "license": "MIT",
     "authors": [
         {
             "name": "Adrian Palmer",
             "email": "adrian.palmer@99designs.com"
+        },
+        {
+            "name": "Ruben de Vries",
+            "email": "ruben@blocktrail.com"
         }
     ],
     "autoload": {
@@ -16,9 +20,9 @@
         }
     },
     "require": {
-        "php": ">=5.3.0",
+        "php": ">=5.4.0",
         "99designs/http-signatures": "~1.1",
-        "guzzle/guzzle": "~3.9"
+        "guzzlehttp/guzzle": "~4.2"
     },
     "require-dev": {
         "phpunit/phpunit": "~4.1"
diff --git a/src/HttpSignatures/Guzzle/Message.php b/src/HttpSignatures/Guzzle/Message.php
deleted file mode 100644
index 5a55452..0000000
--- a/src/HttpSignatures/Guzzle/Message.php
+++ /dev/null
@@ -1,30 +0,0 @@
-<?php
-
-namespace HttpSignatures\Guzzle;
-
-class Message
-{
-    private $request;
-    public $headers;
-
-    public function __construct($request)
-    {
-        $this->request = $request;
-        $this->headers = new MessageHeaders($request);
-    }
-
-    public function getQueryString()
-    {
-        return $this->request->getQuery(true);
-    }
-
-    public function getMethod()
-    {
-        return $this->request->getMethod();
-    }
-
-    public function getPathInfo()
-    {
-        return $this->request->getPath();
-    }
-}
diff --git a/src/HttpSignatures/Guzzle/RequestSubscriber.php b/src/HttpSignatures/Guzzle/RequestSubscriber.php
deleted file mode 100644
index bf28ff2..0000000
--- a/src/HttpSignatures/Guzzle/RequestSubscriber.php
+++ /dev/null
@@ -1,28 +0,0 @@
-<?php
-
-namespace HttpSignatures\Guzzle;
-
-use Guzzle\Common\Event;
-use Symfony\Component\EventDispatcher\EventSubscriberInterface;
-
-class RequestSubscriber implements EventSubscriberInterface
-{
-    private $context;
-
-    function __construct($context)
-    {
-        $this->context = $context;
-    }
-
-    public static function getSubscribedEvents()
-    {
-        return array(
-            'client.create_request' => 'signRequest'
-        );
-    }
-
-    public function signRequest($e)
-    {
-        $this->context->signer()->sign(new Message($e['request']));
-    }
-}
diff --git a/src/HttpSignatures/GuzzleHttp/Message.php b/src/HttpSignatures/GuzzleHttp/Message.php
new file mode 100644
index 0000000..ed9c4fc
--- /dev/null
+++ b/src/HttpSignatures/GuzzleHttp/Message.php
@@ -0,0 +1,47 @@
+<?php
+
+namespace HttpSignatures\GuzzleHttp;
+
+use GuzzleHttp\Message\RequestInterface;
+
+/**
+ * Class RequestMessage
+ *
+ * wrapper around the Guzzle Request instance to have a consistent API for the HttpSignatures classes to consume
+ *
+ * @package HttpSignatures\Guzzle
+ */
+class Message
+{
+    /**
+     * @var RequestInterface
+     */
+    private $request;
+
+    /**
+     * @var MessageHeaders
+     */
+    public $headers;
+
+    public function __construct(RequestInterface $request)
+    {
+        $this->request = $request;
+        $this->headers = new MessageHeaders($request);
+    }
+
+    public function getQueryString()
+    {
+        $qs = $this->request->getQuery();
+        return $qs->count() ? $qs : null;
+    }
+
+    public function getMethod()
+    {
+        return $this->request->getMethod();
+    }
+
+    public function getPathInfo()
+    {
+        return $this->request->getPath();
+    }
+}
diff --git a/src/HttpSignatures/Guzzle/MessageHeaders.php b/src/HttpSignatures/GuzzleHttp/MessageHeaders.php
similarity index 52%
rename from src/HttpSignatures/Guzzle/MessageHeaders.php
rename to src/HttpSignatures/GuzzleHttp/MessageHeaders.php
index 4ff22fd..c1f2547 100644
--- a/src/HttpSignatures/Guzzle/MessageHeaders.php
+++ b/src/HttpSignatures/GuzzleHttp/MessageHeaders.php
@@ -1,12 +1,24 @@
 <?php
 
-namespace HttpSignatures\Guzzle;
+namespace HttpSignatures\GuzzleHttp;
 
+use GuzzleHttp\Message\MessageInterface;
+
+/**
+ * Class MessageHeaders
+ *
+ * wrapper around the Guzzle Request instance to have a consistent API for the HttpSignatures classes to consume
+ *
+ * @package HttpSignatures\Guzzle
+ */
 class MessageHeaders
 {
+    /**
+     * @var MessageInterface
+     */
     private $request;
 
-    public function __construct($request)
+    public function __construct(MessageInterface $request)
     {
         $this->request = $request;
     }
diff --git a/src/HttpSignatures/GuzzleHttp/RequestSubscriber.php b/src/HttpSignatures/GuzzleHttp/RequestSubscriber.php
new file mode 100644
index 0000000..6edaea3
--- /dev/null
+++ b/src/HttpSignatures/GuzzleHttp/RequestSubscriber.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace HttpSignatures\GuzzleHttp;
+
+use GuzzleHttp\Event\BeforeEvent;
+use GuzzleHttp\Event\RequestEvents;
+use GuzzleHttp\Event\SubscriberInterface;
+use HttpSignatures\Context;
+
+class RequestSubscriber implements SubscriberInterface
+{
+    /**
+     * @var \HttpSignatures\Context
+     */
+    private $context;
+
+    public function __construct(Context $context)
+    {
+        $this->context = $context;
+    }
+
+    public function getEvents()
+    {
+        return ['before' => ['onBefore', RequestEvents::SIGN_REQUEST]];
+    }
+
+    public function onBefore(BeforeEvent $event)
+    {
+        $request = $event->getRequest();
+
+        if ($request->getConfig()['auth'] != 'http-signatures') {
+            return;
+        }
+
+        $this->context->signer()->sign(new Message($request));
+    }
+}
diff --git a/tests/GuzzleHttpSignerTest.php b/tests/GuzzleHttpSignerTest.php
new file mode 100644
index 0000000..47da96d
--- /dev/null
+++ b/tests/GuzzleHttpSignerTest.php
@@ -0,0 +1,109 @@
+<?php
+
+namespace HttpSignatures\Test;
+
+use HttpSignatures\GuzzleHttp\Message;
+use HttpSignatures\GuzzleHttp\RequestSubscriber;
+use HttpSignatures\Context;
+
+class GuzzleHttpSignerTest extends \PHPUnit_Framework_TestCase
+{
+    /**
+     * @var Context
+     */
+    private $context;
+
+    /**
+     * @var \GuzzleHttp\Client
+     */
+    private $client;
+
+    public function setUp()
+    {
+        $this->context = new Context(array(
+            'keys' => array('pda' => 'secret'),
+            'algorithm' => 'hmac-sha256',
+            'headers' => array('(request-target)', 'date'),
+        ));
+
+        $this->client = new \GuzzleHttp\Client([
+            'auth' => 'http-signatures'
+        ]);
+        $this->client->getEmitter()->attach(new RequestSubscriber($this->context));
+    }
+
+    /**
+     * test signing a message
+     */
+    public function testGuzzleRequestHasExpectedHeaders()
+    {
+        $message = $this->client->createRequest('GET', '/path?query=123', array(
+            'headers' => array('date' => 'today', 'accept' => 'llamas')
+        ));
+
+        $this->context->signer()->sign(new Message($message));
+
+        $expectedString = implode(
+            ',',
+            array(
+                'keyId="pda"',
+                'algorithm="hmac-sha256"',
+                'headers="(request-target) date"',
+                'signature="SFlytCGpsqb/9qYaKCQklGDvwgmrwfIERFnwt+yqPJw="',
+            )
+        );
+
+        $this->assertEquals(
+            $expectedString,
+            (string) $message->getHeader('Signature')
+        );
+
+        $this->assertEquals(
+            'Signature ' . $expectedString,
+            (string) $message->getHeader('Authorization')
+        );
+    }
+
+    /**
+     * test signing a message with a URL that doesn't contain a ?query
+     */
+    public function testGuzzleRequestHasExpectedHeaders2()
+    {
+        $message = $this->client->createRequest('GET', '/path', array(
+            'headers' => array('date' => 'today', 'accept' => 'llamas')
+        ));
+
+        $this->context->signer()->sign(new Message($message));
+
+        $expectedString = implode(
+            ',',
+            array(
+                'keyId="pda"',
+                'algorithm="hmac-sha256"',
+                'headers="(request-target) date"',
+                'signature="DAtF133khP05pS5Gh8f+zF/UF7mVUojMj7iJZO3Xk4o="',
+            )
+        );
+
+        $this->assertEquals(
+            $expectedString,
+            (string) $message->getHeader('Signature')
+        );
+
+        $this->assertEquals(
+            'Signature ' . $expectedString,
+            (string) $message->getHeader('Authorization')
+        );
+    }
+
+    public function testVerifyGuzzleRequest()
+    {
+        $message = $this->client->createRequest('GET', '/path?query=123', array(
+            'headers' => array('date' => 'today', 'accept' => 'dogs')
+        ));
+
+        $this->context->signer()->sign(new Message($message));
+
+        $this->assertTrue($this->context->verifier()->isValid(new Message($message)));
+    }
+}
diff --git a/tests/GuzzleSignerTest.php b/tests/GuzzleSignerTest.php
deleted file mode 100644
index 6993148..0000000
--- a/tests/GuzzleSignerTest.php
+++ /dev/null
@@ -1,53 +0,0 @@
-<?php
-
-namespace HttpSignatures\Test;
-
-use HttpSignatures\Guzzle\RequestSubscriber;
-use HttpSignatures\Context;
-use HttpSignatures\Guzzle\Message;
-
-class GuzzleSignerTest extends \PHPUnit_Framework_TestCase
-{
-    public function setUp()
-    {
-        $this->context = new Context(array(
-            'keys' => array('pda' => 'secret'),
-            'algorithm' => 'hmac-sha256',
-            'headers' => array('(request-target)', 'date'),
-        ));
-
-        $this->client = new \Guzzle\Http\Client();
-        $this->client->addSubscriber(new RequestSubscriber($this->context));
-    }
-
-    public function testGuzzleRequestHasExpectedHeaders()
-    {
-        $message = $this->client->get('/path?query=123', array('date' => 'today', 'accept' => 'llamas'));
-
-        $expectedString = implode(
-            ',',
-            array(
-                'keyId="pda"',
-                'algorithm="hmac-sha256"',
-                'headers="(request-target) date"',
-                'signature="SFlytCGpsqb/9qYaKCQklGDvwgmrwfIERFnwt+yqPJw="',
-            )
-        );
-
-        $this->assertEquals(
-            $expectedString,
-            (string) $message->getHeader('Signature')
-        );
-
-        $this->assertEquals(
-            'Signature ' . $expectedString,
-            (string) $message->getHeader('Authorization')
-        );
-    }
-
-    public function testVerifyGuzzleRequest()
-    {
-        $message = $this->client->get('/path?query=123', array('date' => 'today', 'accept' => 'dogs'));
-        $this->assertTrue($this->context->verifier()->isValid(new Message($message)));
-    }
-}