diff --git a/src/Symfony/Component/HttpFoundation/Request.php b/src/Symfony/Component/HttpFoundation/Request.php
index 0d5a1110ad..cf6ebbc0b0 100644
--- a/src/Symfony/Component/HttpFoundation/Request.php
+++ b/src/Symfony/Component/HttpFoundation/Request.php
@@ -1497,7 +1497,7 @@ class Request
      * if the proxy is trusted (see "setTrustedProxies()"), otherwise it returns
      * the latter (from the "SERVER_PROTOCOL" server parameter).
      *
-     * @return string
+     * @return string|null
      */
     public function getProtocolVersion()
     {