--- a/dom/alarm/AlarmService.jsm
+++ b/dom/alarm/AlarmService.jsm
@@ -223,34 +223,34 @@ let AlarmService = {
       ppmm.sendAsyncMessage("AlarmsManager:" + aMessageName, json);
   },
 
   _onAlarmFired: function _onAlarmFired() {
     debug("_onAlarmFired()");
 
     if (this._currentAlarm) {
       debug("Fire system intent: " + JSON.stringify(this._currentAlarm));
-      if (this._currentAlarm.manifestURL)
-        messenger.sendMessage("alarm", this._currentAlarm, this._currentAlarm.manifestURL);
+      let manifestURI = Services.io.newURI(this._currentAlarm.manifestURL, null, null);
+      messenger.sendMessage("alarm", this._currentAlarm, manifestURI);
       this._currentAlarm = null;
     }
 
     // reset the next alarm from the queue
     let nowTime = Date.now();
     let alarmQueue = this._alarmQueue;
     while (alarmQueue.length > 0) {
       let nextAlarm = alarmQueue.shift();
       let nextAlarmTime = this._getAlarmTime(nextAlarm);
 
       // if the next alarm has been expired, directly 
       // fire system intent for it instead of setting it
       if (nextAlarmTime <= nowTime) {
         debug("Fire system intent: " + JSON.stringify(nextAlarm));
-        if (nextAlarm.manifestURL)
-          messenger.sendMessage("alarm", nextAlarm, nextAlarm.manifestURL);
+        let manifestURI = Services.io.newURI(nextAlarm.manifestURL, null, null);
+        messenger.sendMessage("alarm", nextAlarm, manifestURI);
       } else {
         this._currentAlarm = nextAlarm;
         break;
       }
     }
     this._debugCurrentAlarm();
   },
 

--- a/dom/alarm/AlarmsManager.js
+++ b/dom/alarm/AlarmsManager.js
@@ -40,16 +40,21 @@ AlarmsManager.prototype = {
                                       contractID: ALARMSMANAGER_CONTRACTID,
                                       classDescription: "AlarmsManager",
                                       interfaces: [nsIDOMMozAlarmsManager],
                                       flags: nsIClassInfo.DOM_OBJECT }),
 
   add: function add(aDate, aRespectTimezone, aData) {
     debug("add()");
 
+    if (!this._manifestURL) {
+      debug("Cannot add alarms for non-installed apps.");
+      throw Components.results.NS_ERROR_FAILURE;
+    }
+
     let isIgnoreTimezone = true;
     switch (aRespectTimezone) {
       case "honorTimezone":
         isIgnoreTimezone = false;
         break;
 
       case "ignoreTimezone":
         isIgnoreTimezone = true;
@@ -145,18 +150,17 @@ AlarmsManager.prototype = {
     this._cpmm = Cc["@mozilla.org/childprocessmessagemanager;1"].getService(Ci.nsISyncMessageSender);
 
     // Add the valid messages to be listened.
     this.initHelper(aWindow, ["AlarmsManager:Add:Return:OK", "AlarmsManager:Add:Return:KO", 
                               "AlarmsManager:GetAll:Return:OK", "AlarmsManager:GetAll:Return:KO"]);
 
     // Get the manifest URL if this is an installed app
     this._manifestURL = null;
-    let utils = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
-                       .getInterface(Components.interfaces.nsIDOMWindowUtils);
+    let utils = aWindow.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
     let app = utils.getApp();
     if (app)
       this._manifestURL = app.manifestURL;
   },
 
   // Called from DOMRequestIpcHelper.
   uninit: function uninit() {
     debug("uninit()");