diff --git a/include/functions_images.inc.php b/include/functions_images.inc.php
index 67f4b4c0..16cbb268 100644
--- a/include/functions_images.inc.php
+++ b/include/functions_images.inc.php
@@ -947,6 +947,7 @@ function serendipity_guessMime($extension) {
             break;
 
         case 'mov':
+        case 'mp4':
         case 'qt':
             $mime = 'video/x-quicktime';
             break;