diff --git a/widget/nsIPrintSettingsWin.idl b/widget/nsIPrintSettingsWin.idl
index 2325f370f555e..1a61a7f8ce2f1 100644
--- a/widget/nsIPrintSettingsWin.idl
+++ b/widget/nsIPrintSettingsWin.idl
@@ -18,7 +18,7 @@
 /**
  * Simplified PrintSettings for Windows interface
  */
-[scriptable, uuid(c63eed41-6ac5-459e-8a64-033eb9ad770a)]
+[uuid(c63eed41-6ac5-459e-8a64-033eb9ad770a)]
 interface nsIPrintSettingsWin : nsISupports
 {
   /**
diff --git a/widget/nsITaskbarTabPreview.idl b/widget/nsITaskbarTabPreview.idl
index 73a13913de958..b56239ed85e66 100644
--- a/widget/nsITaskbarTabPreview.idl
+++ b/widget/nsITaskbarTabPreview.idl
@@ -20,7 +20,7 @@ interface imgIContainer;
  * An application may have as many tab previews per window as memory allows.
  *
  */
-[scriptable, uuid(11E4C8BD-5C2D-4E1A-A9A1-79DD5B0FE544)]
+[scriptable, builtinclass, uuid(11E4C8BD-5C2D-4E1A-A9A1-79DD5B0FE544)]
 interface nsITaskbarTabPreview : nsITaskbarPreview
 {
   /**