diff --git a/toolkit/components/printing/content/printUtils.js b/toolkit/components/printing/content/printUtils.js
index bdd2823608ba..6c25e1184f13 100644
--- a/toolkit/components/printing/content/printUtils.js
+++ b/toolkit/components/printing/content/printUtils.js
@@ -205,7 +205,9 @@ var PrintUtils = {
 
     QueryInterface : function(iid)
     {
-      if (iid.equals(Components.interfaces.nsIObserver) || iid.equals(Components.interfaces.nsISupportsWeakReference))
+      if (iid.equals(Components.interfaces.nsIObserver) ||
+          iid.equals(Components.interfaces.nsISupportsWeakReference) ||
+          iid.equals(Components.interfaces.nsISupports))
         return this;   
       throw Components.results.NS_NOINTERFACE;
     }