--- a/b2g/chrome/content/shell.js
+++ b/b2g/chrome/content/shell.js
@@ -1000,19 +1000,21 @@ window.addEventListener('ContentStart', 
       shell.submitCrash(e.detail.crashID);
     }
   });
 });
 
 window.addEventListener('ContentStart', function update_onContentStart() {
   let updatePrompt = Cc["@mozilla.org/updates/update-prompt;1"]
                        .createInstance(Ci.nsIUpdatePrompt);
+  if (!updatePrompt) {
+    return;
+  }
 
-  let content = shell.contentBrowser.contentWindow;
-  content.addEventListener("mozContentEvent", updatePrompt.wrappedJSObject);
+  updatePrompt.wrappedJSObject.handleContentStart(shell);
 });
 
 (function geolocationStatusTracker() {
   let gGeolocationActiveCount = 0;
 
   Services.obs.addObserver(function(aSubject, aTopic, aData) {
     let oldCount = gGeolocationActiveCount;
     if (aData == "starting") {

--- a/b2g/components/UpdatePrompt.js
+++ b/b2g/components/UpdatePrompt.js
@@ -113,25 +113,36 @@ UpdatePrompt.prototype = {
                                          Ci.nsIProgressEventSink,
                                          Ci.nsIObserver]),
   _xpcom_factory: XPCOMUtils.generateSingletonFactory(UpdatePrompt),
 
   _update: null,
   _applyPromptTimer: null,
   _waitingForIdle: false,
   _updateCheckListner: null,
+  _pendingEvents: [],
 
   get applyPromptTimeout() {
     return Services.prefs.getIntPref(PREF_APPLY_PROMPT_TIMEOUT);
   },
 
   get applyIdleTimeout() {
     return Services.prefs.getIntPref(PREF_APPLY_IDLE_TIMEOUT);
   },
 
+  handleContentStart: function UP_handleContentStart(shell) {
+    let content = shell.contentBrowser.contentWindow;
+    content.addEventListener("mozContentEvent", this);
+
+    for (let i = 0; i < this._pendingEvents.length; i++) {
+      shell.sendChromeEvent(this._pendingEvents[i]);
+    }
+    this._pendingEvents.length = 0;
+  },
+
   // nsIUpdatePrompt
 
   // FIXME/bug 737601: we should have users opt-in to downloading
   // updates when on a billed pipe.  Initially, opt-in for 3g, but
   // that doesn't cover all cases.
   checkForUpdates: function UP_checkForUpdates() { },
 
   showUpdateAvailable: function UP_showUpdateAvailable(aUpdate) {
@@ -232,26 +243,27 @@ UpdatePrompt.prototype = {
       log("Warning: no patches available in update");
     }
 
     this._update = aUpdate;
     return this.sendChromeEvent(aType, detail);
   },
 
   sendChromeEvent: function UP_sendChromeEvent(aType, aDetail) {
+    let detail = aDetail || {};
+    detail.type = aType;
+
     let browser = Services.wm.getMostRecentWindow("navigator:browser");
     if (!browser) {
+      this._pendingEvents.push(detail);
       log("Warning: Couldn't send update event " + aType +
-          ": no content browser");
+          ": no content browser. Will send again when content becomes available.");
       return false;
     }
 
-    let detail = aDetail || {};
-    detail.type = aType;
-
     browser.shell.sendChromeEvent(detail);
     return true;
   },
 
   handleAvailableResult: function UP_handleAvailableResult(aDetail) {
     // If the user doesn't choose "download", the updater will implicitly call
     // showUpdateAvailable again after a certain period of time
     switch (aDetail.result) {