From df6d85ca3ce59af1826c1196a88a99656b8eb616 Mon Sep 17 00:00:00 2001
From: Kris Maglione <maglione.k@gmail.com>
Date: Tue, 14 Feb 2012 20:30:53 -0500
Subject: [PATCH] Bug 718255 yay.

---
 common/modules/prefs.jsm | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/common/modules/prefs.jsm b/common/modules/prefs.jsm
index 8df88684..3f865b61 100644
--- a/common/modules/prefs.jsm
+++ b/common/modules/prefs.jsm
@@ -26,7 +26,8 @@ var Prefs = Module("prefs", XPCOM([Ci.nsIObserver, Ci.nsISupportsWeakReference])
         this._prefContexts = [];
 
         this.branch = services.pref[defaults ? "getDefaultBranch" : "getBranch"](branch || "");
-        this.branch instanceof Ci.nsIPrefBranch2;
+        if ("nsIPrefBranch2" in Ci)
+            this.branch instanceof Ci.nsIPrefBranch2;
 
         this.defaults = defaults ? this : this.constructor(branch, true);