diff --git a/core/lib/Drupal/Core/Routing/NonAdminRoutesPreloader.php b/core/lib/Drupal/Core/Routing/NonAdminRoutesPreloader.php
index d9dcd77..a478c94 100644
--- a/core/lib/Drupal/Core/Routing/NonAdminRoutesPreloader.php
+++ b/core/lib/Drupal/Core/Routing/NonAdminRoutesPreloader.php
@@ -14,7 +14,11 @@
 use Symfony\Component\HttpKernel\KernelEvents;
 
 /**
- * Defines a class which preloads non admin routes.
+ * Defines a class which preloads non-admin routes.
+ *
+ * On an actual site we want to avoid too many database queries so we build a
+ * list of all routes which most likely appear on the actual site, which are all
+ * HTML routes not starting with "/admin".
  */
 class NonAdminRoutesPreloader implements EventSubscriberInterface {
 
@@ -82,13 +86,13 @@ protected function getNonAdminRoutes() {
   }
 
   /**
-   * Load all the admin routes right before the actual page is rendered.
+   * Loads all non-admin routes right before the actual page is rendered.
    *
    * @param \Symfony\Component\HttpKernel\Event\KernelEvent $event
-   *   The Event to process.
+   *   The event to process.
    */
   public function onRequest(KernelEvent $event) {
-    // Just preload on normal html pages, as they will contain the menu links.
+    // Just preload on normal HTML pages, as they will display menu links.
     if ($this->negotiation->getContentType($event->getRequest()) == 'html') {
       $this->loadNonAdminRoutes();
     }
@@ -104,16 +108,16 @@ protected function loadNonAdminRoutes() {
   }
 
   /**
-   * Alters existing routes for a specific collection.
+   * Store the non admin routes in state when the route building is finished.
    *
    * @param \Drupal\Core\Routing\RouteBuildEvent $event
    *   The route build event.
    */
-  public function onAlterRoutes(RouteBuildEvent $event) {
+  public function onFinishedRoutes(RouteBuildEvent $event) {
     $collection = $event->getRouteCollection();
     foreach ($collection->all() as $name => $route) {
-      // Just preload non admin and _content routes, as they are the ones
-      // that appear on menu links and co.
+      // Just preload non-admin and _content routes, as they are the ones that
+      // are used on menu links.
       if (strpos($route->getPath(), '/admin') === FALSE && $route->hasDefault('_content')) {
         $this->nonAdminRoutesOnRebuild[] = $name;
       }
@@ -126,8 +130,9 @@ public function onAlterRoutes(RouteBuildEvent $event) {
    * {@inheritdoc}
    */
   public static function getSubscribedEvents() {
-    $events[RoutingEvents::ALTER] = array('onAlterRoutes', -1024);
-    // Come before the HtmlViewSubscriber.
+    $events[RoutingEvents::FINISHED] = array('onFinishedRoutes');
+    // Load the routes before the controller is executed (which happens after
+    // the kernel request event).
     $events[KernelEvents::REQUEST][] = array('onRequest');
     return $events;
   }