diff --git a/core/modules/system/css/system.theme.css b/core/modules/system/css/system.theme.css
index 3a8bddb..3ddb888 100644
--- a/core/modules/system/css/system.theme.css
+++ b/core/modules/system/css/system.theme.css
@@ -169,7 +169,8 @@ abbr.ajax-changed {
  * Markup generated by feed-icon.html.twig.
  */
 .feed-icon {
-  background: url(../../../misc/feed.png) no-repeat;
+  background-image: url(../../../misc/feed.png);
+  background-repeat: no-repeat;
   overflow: hidden;
   text-indent: -9999px;
   display: block;