diff --git a/toolkit/themes/winstripe/mozapps/extensions/about.css b/toolkit/themes/winstripe/mozapps/extensions/about.css
index c605e944a9a..fa8e0681c55 100644
--- a/toolkit/themes/winstripe/mozapps/extensions/about.css
+++ b/toolkit/themes/winstripe/mozapps/extensions/about.css
@@ -15,6 +15,10 @@
     -moz-appearance: -moz-win-glass;
     background: transparent;
   }
+
+  #clientBox {
+    -moz-appearance: -moz-win-exclude-glass;
+  }
 }