diff --git a/dom/base/DOMRequestHelper.jsm b/dom/base/DOMRequestHelper.jsm
index 869a21025a56..0184999b9419 100644
--- a/dom/base/DOMRequestHelper.jsm
+++ b/dom/base/DOMRequestHelper.jsm
@@ -52,7 +52,8 @@ DOMRequestIpcHelper.prototype = {
    * queryInterface method and adds at least one weak listener to the Message
    * Manager MUST implement Ci.nsISupportsWeakReference.
    */
-  QueryInterface: XPCOMUtils.generateQI([Ci.nsISupportsWeakReference]),
+  QueryInterface: XPCOMUtils.generateQI([Ci.nsISupportsWeakReference,
+                                         Ci.nsIObserver]),
 
    /**
    *  'aMessages' is expected to be an array of either:
diff --git a/dom/messages/SystemMessageManager.js b/dom/messages/SystemMessageManager.js
index abc5b2f31bb9..44e6a93e7afd 100644
--- a/dom/messages/SystemMessageManager.js
+++ b/dom/messages/SystemMessageManager.js
@@ -284,6 +284,9 @@ SystemMessageManager.prototype = {
     if (aTopic === kSystemMessageInternalReady) {
       this._registerManifest();
     }
+
+    // Call the DOMRequestIpcHelper.observe method.
+    this.__proto__.__proto__.observe.call(this, aSubject, aTopic, aData);
   },
 
   _registerManifest: function sysMessMgr_registerManifest() {