diff --git a/src/Symfony/Component/HttpFoundation/Request.php b/src/Symfony/Component/HttpFoundation/Request.php
index e1309d477b..7e8e075a83 100644
--- a/src/Symfony/Component/HttpFoundation/Request.php
+++ b/src/Symfony/Component/HttpFoundation/Request.php
@@ -1322,7 +1322,7 @@ class Request
      *
      * @param string $format The format
      *
-     * @return string The associated mime type (null if not found)
+     * @return string|null The associated mime type (null if not found)
      */
     public function getMimeType($format)
     {