diff --git a/chrome/content/zotero/xpcom/cookieSandbox.js b/chrome/content/zotero/xpcom/cookieSandbox.js
index be3906978f..0b8da0efbf 100755
--- a/chrome/content/zotero/xpcom/cookieSandbox.js
+++ b/chrome/content/zotero/xpcom/cookieSandbox.js
@@ -170,7 +170,10 @@ Zotero.CookieSandbox.prototype = {
 	 * @param {nsIInterfaceRequestor} ir
 	 */
 	"attachToInterfaceRequestor": function(ir) {
-		Zotero.CookieSandbox.Observer.trackedInterfaceRequestors.set(ir.QueryInterface(Components.interfaces.nsIInterfaceRequestor), this);
+		if (typeof ir.QueryInterface === 'function') {
+			ir = ir.QueryInterface(Components.interfaces.nsIInterfaceRequestor);
+		}
+		Zotero.CookieSandbox.Observer.trackedInterfaceRequestors.set(ir, this);
 	},
 	
 	/**
@@ -413,4 +416,4 @@ Zotero.CookieSandbox.Observer = new function() {
 			Zotero.debug("CookieSandbox: Slurped cookies from "+channelURI, 5);
 		}
 	}
-}
\ No newline at end of file
+}