diff --git a/mozilla/xpfe/components/sidebar/src/nsSidebar.js b/mozilla/xpfe/components/sidebar/src/nsSidebar.js
index 7395615d854..620e5e49a7d 100644
--- a/mozilla/xpfe/components/sidebar/src/nsSidebar.js
+++ b/mozilla/xpfe/components/sidebar/src/nsSidebar.js
@@ -331,6 +331,12 @@ nsSidebar.prototype.flags = nsIClassInfo.DOM_OBJECT;
 // property of nsIClassInfo
 nsSidebar.prototype.classDescription = "Sidebar";
 
+// method of nsIClassInfo
+nsSidebar.prototype.getInterfaces = function(c) {c.value = 0; return null;}
+
+// method of nsIClassInfo
+nsSidebar.prototype.getHelperForLanguage = function() {return null;}
+
 nsSidebar.prototype.QueryInterface =
 function (iid) {
     if (!iid.equals(nsISidebar) &&