diff --git a/webapprt/Startup.jsm b/webapprt/Startup.jsm
index b27b85e41924..fbaef25c363c 100644
--- a/webapprt/Startup.jsm
+++ b/webapprt/Startup.jsm
@@ -12,17 +12,24 @@ this.EXPORTED_SYMBOLS = ["startup"];
 const Ci = Components.interfaces;
 const Cu = Components.utils;
 
+/* We load here modules that are needed to perform the application startup.
+ * We lazily load modules that aren't needed on every startup.
+ * We load modules that aren't used here but that need to perform some
+ * initialization steps later in the startup function. */
+
+Cu.import("resource://gre/modules/XPCOMUtils.jsm");
 Cu.import("resource://gre/modules/Services.jsm");
-Cu.import("resource://gre/modules/AppsUtils.jsm");
-Cu.import("resource://gre/modules/PermissionsInstaller.jsm");
-Cu.import('resource://gre/modules/Payment.jsm');
-Cu.import('resource://gre/modules/AlarmService.jsm');
 Cu.import("resource://gre/modules/Task.jsm");
 Cu.import("resource://gre/modules/Promise.jsm");
 Cu.import("resource://gre/modules/osfile.jsm");
 
 Cu.import("resource://webapprt/modules/WebappRT.jsm");
-Cu.import("resource://webapprt/modules/WebRTCHandler.jsm");
+
+// Lazily load these modules because we don't need them at every
+// startup, but only during first run or runtime update.
+
+XPCOMUtils.defineLazyModuleGetter(this, "PermissionsInstaller",
+  "resource://gre/modules/PermissionsInstaller.jsm");
 
 const PROFILE_DIR = OS.Constants.Path.profileDir;
 
@@ -135,6 +142,12 @@ this.startup = function(window) {
     // Wait for XUL window loading
     yield deferredWindowLoad.promise;
 
+    // Load these modules here because they aren't needed right at startup,
+    // but they need to be loaded to perform some initialization steps.
+    Cu.import("resource://gre/modules/Payment.jsm");
+    Cu.import("resource://gre/modules/AlarmService.jsm");
+    Cu.import("resource://webapprt/modules/WebRTCHandler.jsm");
+
     // Get the <browser> element in the webapp.xul window.
     let appBrowser = window.document.getElementById("content");