diff --git a/src/Symfony/Component/HttpFoundation/Response.php b/src/Symfony/Component/HttpFoundation/Response.php
index 65d435ba5d..c65ceb7163 100644
--- a/src/Symfony/Component/HttpFoundation/Response.php
+++ b/src/Symfony/Component/HttpFoundation/Response.php
@@ -109,6 +109,7 @@ class Response
         428 => 'Precondition Required',                                       // RFC6585
         429 => 'Too Many Requests',                                           // RFC6585
         431 => 'Request Header Fields Too Large',                             // RFC6585
+        451 => 'Unavailable For Legal Reasons',
         500 => 'Internal Server Error',
         501 => 'Not Implemented',
         502 => 'Bad Gateway',