diff --git a/app/assets/stylesheets/zammad.css.scss b/app/assets/stylesheets/zammad.css.scss
index f101f0110..9d18ab2a7 100644
--- a/app/assets/stylesheets/zammad.css.scss
+++ b/app/assets/stylesheets/zammad.css.scss
@@ -733,16 +733,17 @@ textarea,
     Firefox only hack
     -----------------
 
-    Firefox doesn't allow us to hide the dropdown arrow
-    but we want to replace it with our own icon.
-    So we have to hide our own icon in Firefox.
+    Firefox below version 35 doesn't allow us to 
+    hide the dropdown arrow but we want to replace 
+    it with our own icon. So we have to hide our own 
+    icon in Firefox versions under 35.
+    
+    The class is set via Javascript
 
   */
 
-  @-moz-document url-prefix() {
-    .form-control + .select-arrow {
-      display: none;
-    }
+  html.ff-lt-35 .form-control + .select-arrow {
+    display: none;
   }
 
   select::-ms-expand {