diff --git a/b2g/app/b2g.js b/b2g/app/b2g.js
index 1acd08571d7d..f4e154b40268 100644
--- a/b2g/app/b2g.js
+++ b/b2g/app/b2g.js
@@ -755,7 +755,11 @@ pref("network.activity.blipIntervalMilliseconds", 250);
 // can be flipped to false.
 pref("network.gonk.manage-offline-status", true);
 
+// On Firefox Mulet, we can't enable shared JSM scope
+// as it breaks most Firefox JSMs (see bug 961777)
+#ifndef MOZ_MULET
 pref("jsloader.reuseGlobal", true);
+#endif
 
 // Enable font inflation for browser tab content.
 pref("font.size.inflation.minTwips", 120);
diff --git a/js/xpconnect/loader/mozJSComponentLoader.cpp b/js/xpconnect/loader/mozJSComponentLoader.cpp
index 7a71fbedbe32..989ce232003d 100644
--- a/js/xpconnect/loader/mozJSComponentLoader.cpp
+++ b/js/xpconnect/loader/mozJSComponentLoader.cpp
@@ -351,7 +351,8 @@ mozJSComponentLoader::ReallyInit()
 
     // XXXkhuey B2G child processes have some sort of preferences race that
     // results in getting the wrong value.
-#ifdef MOZ_B2G
+    // But we don't want that on Firefox Mulet as it break most Firefox JSMs...
+#if defined(MOZ_B2G) && !defined(MOZ_MULET)
     mReuseLoaderGlobal = true;
 #endif