/**
  * (non-PHPdoc)
  * @see ObjectStorage_Abstract::update()
  */
 public function update()
 {
     $headers = $this->request->getHeaders();
     if (count($headers) > 0) {
         foreach ($headers as $key => $value) {
             if (in_array(strtoupper($key), self::$skipOverwriteHeaders)) {
                 $this->request->deleteHeader($key);
             }
         }
     }
     return parent::update();
 }