diff --git a/lib/Github/Exception/ApiLimitExceedException.php b/lib/Github/Exception/ApiLimitExceedException.php
index a9b5454f714..851631cccf8 100644
--- a/lib/Github/Exception/ApiLimitExceedException.php
+++ b/lib/Github/Exception/ApiLimitExceedException.php
@@ -9,7 +9,7 @@
  */
 class ApiLimitExceedException extends RuntimeException
 {
-    public function __construct($limit, $code = 0, $previous = null)
+    public function __construct($limit = 5000, $code = 0, $previous = null)
     {
         parent::__construct('You have reached GitHub hour limit! Actual limit is: '. $limit, $code, $previous);
     }
diff --git a/lib/Github/HttpClient/CachedHttpClient.php b/lib/Github/HttpClient/CachedHttpClient.php
index 16457bd0683..f28f54bd9e2 100644
--- a/lib/Github/HttpClient/CachedHttpClient.php
+++ b/lib/Github/HttpClient/CachedHttpClient.php
@@ -47,7 +47,7 @@ public function request($path, array $parameters = array(), $httpMethod = 'GET',
         $response = parent::request($path, $parameters, $httpMethod, $headers);
 
         $key = trim($this->options['base_url'].$path, '/');
-        if ($response->isNotModified()) {
+        if (304 == $response->getStatusCode()) {
             return $this->getCache()->get($key);
         }
 
@@ -64,7 +64,13 @@ public function request($path, array $parameters = array(), $httpMethod = 'GET',
     protected function createRequest($httpMethod, $url)
     {
         $request = parent::createRequest($httpMethod, $url);
-        $request->addHeader(sprintf('If-Modified-Since: %s', date('r', $this->getCache()->getModifiedSince($url))));
+
+        if ($modifiedAt = $this->getCache()->getModifiedSince($url)) {
+            $modifiedAt = new \DateTime('@'.$modifiedAt);
+            $modifiedAt->setTimezone(new \DateTimeZone('GMT'));
+
+            $request->addHeader(sprintf('If-Modified-Since: %s GMT', $modifiedAt->format('l, d-M-y H:i:s')));
+        }
 
         return $request;
     }
diff --git a/lib/Github/HttpClient/Message/Response.php b/lib/Github/HttpClient/Message/Response.php
index 35f2ada5264..c039ac4bae6 100644
--- a/lib/Github/HttpClient/Message/Response.php
+++ b/lib/Github/HttpClient/Message/Response.php
@@ -3,7 +3,6 @@
 namespace Github\HttpClient\Message;
 
 use Buzz\Message\Response as BaseResponse;
-
 use Github\Exception\ApiLimitExceedException;
 
 class Response extends BaseResponse
@@ -55,23 +54,13 @@ public function getPagination()
      */
     public function getApiLimit()
     {
-        $header = $this->getHeaderAttributes('X-RateLimit-Remaining');
+        $header = $this->getHeader('X-RateLimit-Remaining');
         if (!empty($header)) {
             $this->remainingCalls = $header;
         }
 
         if (null !== $this->remainingCalls && 1 > $this->remainingCalls) {
-            throw new ApiLimitExceedException($this->options['api_limit']);
+            throw new ApiLimitExceedException($this->getHeader('X-RateLimit-Limit'));
         }
     }
-
-    /**
-     * Is not modified
-     *
-     * @return Boolean
-     */
-    public function isNotModified()
-    {
-        return 304 === $this->getStatusCode();
-    }
 }