--- a/dom/commandhandler/nsICommandParams.idl
+++ b/dom/commandhandler/nsICommandParams.idl
@@ -6,17 +6,17 @@
 #include "nsISupports.idl"
 
 /*
  * nsICommandParams is used to pass parameters to commands executed
  * via nsICommandManager, and to get command state.
  *
  */
 
-[scriptable, uuid(b1fdf3c4-74e3-4f7d-a14d-2b76bcf53482)]
+[scriptable, builtinclass, uuid(b1fdf3c4-74e3-4f7d-a14d-2b76bcf53482)]
 interface nsICommandParams : nsISupports
 {
   /*
    * List of primitive types for parameter values.
    */
   const short eNoType                     = 0;      /* Only used for sanity checking */
   const short eBooleanType                = 1;
   const short eLongType                   = 2;