diff --git a/dom/apps/src/Webapps.jsm b/dom/apps/src/Webapps.jsm
index a87d4f5f40a5..55087ae1e896 100644
--- a/dom/apps/src/Webapps.jsm
+++ b/dom/apps/src/Webapps.jsm
@@ -44,6 +44,11 @@ XPCOMUtils.defineLazyGetter(this, "msgmgr", function() {
          .getService(Ci.nsISystemMessagesInternal);
 });
 
+XPCOMUtils.defineLazyGetter(this, "updateSvc", function() {
+  return Cc["@mozilla.org/offlinecacheupdate-service;1"]
+           .getService(Ci.nsIOfflineCacheUpdateService);
+});
+
 #ifdef MOZ_WIDGET_GONK
   const DIRECTORY_NAME = "webappsDir";
 #elifdef ANDROID
@@ -931,8 +936,6 @@ this.DOMApplicationRegistry = {
     // if the manifest has an appcache_path property, use it to populate the appcache
     if (aManifest.appcache_path) {
       let appcacheURI = Services.io.newURI(aManifest.fullAppcachePath(), null, null);
-      let updateService = Cc["@mozilla.org/offlinecacheupdate-service;1"]
-                            .getService(Ci.nsIOfflineCacheUpdateService);
       let docURI = Services.io.newURI(aManifest.fullLaunchPath(), null, null);
       // We determine the app's 'installState' according to its previous
       // state. Cancelled download should remain as 'pending'. Successfully
@@ -943,8 +946,9 @@ this.DOMApplicationRegistry = {
       // We set the 'downloading' flag right before starting the app
       // download/update.
       aApp.downloading = true;
-      let cacheUpdate = aProfileDir ? updateService.scheduleCustomProfileUpdate(appcacheURI, docURI, aProfileDir)
-                                    : updateService.scheduleAppUpdate(appcacheURI, docURI, aApp.localId, false);
+      let cacheUpdate = aProfileDir
+        ? updateSvc.scheduleCustomProfileUpdate(appcacheURI, docURI, aProfileDir)
+        : updateSvc.scheduleAppUpdate(appcacheURI, docURI, aApp.localId, false);
       cacheUpdate.addObserver(new AppcacheObserver(aApp), false);
       if (aOfflineCacheObserver) {
         cacheUpdate.addObserver(aOfflineCacheObserver, false);
@@ -1038,9 +1042,23 @@ this.DOMApplicationRegistry = {
 
       this._saveApps(function() {
         aData.app = app;
-        aData.event = manifest.appcache_path ? "downloadavailable"
-                                             : "downloadapplied";
-        aMm.sendAsyncMessage("Webapps:CheckForUpdate:Return:OK", aData);
+        if (!manifest.appcache_path) {
+          aData.event = "downloadapplied";
+          aMm.sendAsyncMessage("Webapps:CheckForUpdate:Return:OK", aData);
+        } else {
+          // Check if the appcache is updatable, and send "downloadavailable" or
+          // "downloadapplied".
+          let updateObserver = {
+            observe: function(aSubject, aTopic, aData) {
+              aData.event =
+                aTopic == "offline-cache-update-available" ? "downloadavailable"
+                                                           : "downloadapplied";
+              aMm.sendAsyncMessage("Webapps:CheckForUpdate:Return:OK", aData);
+            }
+          }
+          updateSvc.checkForUpdate(Services.io.newURI(aData.manifestURL, null, null),
+                                   app.localId, false, updateObserver);
+        }
       });
 
       // Update the permissions for this app.