diff --git a/toolkit/components/startup/public/nsIAppStartup.idl b/toolkit/components/startup/public/nsIAppStartup.idl
index f9a3f585c156..25789971925f 100644
--- a/toolkit/components/startup/public/nsIAppStartup.idl
+++ b/toolkit/components/startup/public/nsIAppStartup.idl
@@ -41,7 +41,7 @@
 
 interface nsICmdLineService;
 
-[scriptable, uuid(e9b0f89b-0529-4d96-98a8-eb5b2b9a8383)]
+[scriptable, uuid(6799abed-4721-4f51-9304-d1a2ea1df5d5)]
 interface nsIAppStartup : nsISupports
 {
     /**
@@ -49,6 +49,12 @@ interface nsIAppStartup : nsISupports
      */
     void createHiddenWindow();
 
+    /**
+     * Destroys the hidden window. This will have no effect if the hidden window
+     * has not yet been created.
+     */
+    void destroyHiddenWindow();
+
     /**
      * Runs an application event loop: normally the main event pump which
      * defines the lifetime of the application. If there are no windows open
diff --git a/toolkit/components/startup/src/nsAppStartup.cpp b/toolkit/components/startup/src/nsAppStartup.cpp
index 667e6d0340a6..e62fbb585904 100644
--- a/toolkit/components/startup/src/nsAppStartup.cpp
+++ b/toolkit/components/startup/src/nsAppStartup.cpp
@@ -150,6 +150,17 @@ nsAppStartup::CreateHiddenWindow()
 }
 
 
+NS_IMETHODIMP
+nsAppStartup::DestroyHiddenWindow()
+{
+  nsCOMPtr<nsIAppShellService> appShellService
+    (do_GetService(NS_APPSHELLSERVICE_CONTRACTID));
+  NS_ENSURE_TRUE(appShellService, NS_ERROR_FAILURE);
+
+  return appShellService->DestroyHiddenWindow();
+}
+
+
 NS_IMETHODIMP
 nsAppStartup::Run(void)
 {
@@ -300,12 +311,6 @@ nsAppStartup::Quit(PRUint32 aMode)
         mRestart ? restartStr.get() : shutdownStr.get());
     }
 
-    nsCOMPtr<nsIAppShellService> appShellService
-      (do_GetService(NS_APPSHELLSERVICE_CONTRACTID));
-    NS_ASSERTION(appShellService, "We're gonna leak something.");
-    if (appShellService)
-      appShellService->DestroyHiddenWindow();
-
     if (!mRunning) {
       postedExitEvent = PR_TRUE;
     }
diff --git a/toolkit/xre/nsAppRunner.cpp b/toolkit/xre/nsAppRunner.cpp
index 838e827c53ae..4b8b81797215 100644
--- a/toolkit/xre/nsAppRunner.cpp
+++ b/toolkit/xre/nsAppRunner.cpp
@@ -850,6 +850,10 @@ private:
 ScopedXPCOMStartup::~ScopedXPCOMStartup()
 {
   if (mServiceManager) {
+    nsCOMPtr<nsIAppStartup> appStartup (do_GetService(NS_APPSTARTUP_CONTRACTID));
+    if (appStartup)
+      appStartup->DestroyHiddenWindow();
+
     gDirServiceProvider->DoShutdown();
 
     WriteConsoleLog();
@@ -3182,12 +3186,6 @@ XRE_main(int argc, char* argv[], const nsXREAppData* aAppData)
 #ifdef XP_MACOSX
           SetupMacCommandLine(gRestartArgc, gRestartArgv);
 #endif
-
-          // Ensure hidden window is destroyed before xpcom shuts down
-          nsCOMPtr<nsIAppShellService> appShellService
-                  (do_GetService(NS_APPSHELLSERVICE_CONTRACTID));
-          if (appShellService)
-            appShellService->DestroyHiddenWindow();
         }
       }
     }