diff --git a/ed/idl/mediaqueries-5.idl b/ed/idl/mediaqueries-5.idl
index 24f1aa6346b5..c951c356ca3c 100644
--- a/ed/idl/mediaqueries-5.idl
+++ b/ed/idl/mediaqueries-5.idl
@@ -5,7 +5,7 @@
 
 typedef (MediaList or boolean) CustomMediaQuery;
 
-[Exposed=Window, RuntimeEnabled=CSSCustomMedia]
+[Exposed=Window]
 interface CSSCustomMediaRule : CSSRule {
     readonly attribute CSSOMString name;
     readonly attribute CustomMediaQuery query;