diff --git a/core/lib/Drupal/Core/EventSubscriber/OptionsRequestSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/OptionsRequestSubscriber.php
index a3d38da..622fe23 100644
--- a/core/lib/Drupal/Core/EventSubscriber/OptionsRequestSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/OptionsRequestSubscriber.php
@@ -64,6 +64,7 @@ public function onRequest(GetResponseEvent $event) {
    * {@inheritdoc}
    */
   public static function getSubscribedEvents() {
+    // Set a high priority so its executed before routing.
     $events[KernelEvents::REQUEST][] = ['onRequest', 1000] ;
     return $events;
   }