diff --git a/less/progress-bars.less b/less/progress-bars.less
index cfca78d683..eeb14eef74 100644
--- a/less/progress-bars.less
+++ b/less/progress-bars.less
@@ -11,6 +11,7 @@
   to    { background-position: 40px 0; }
 }
 
+// Firefox
 @-moz-keyframes progress-bar-stripes {
   from  { background-position: 0 0; }
   to    { background-position: 40px 0; }