diff --git a/core/modules/system/src/Controller/Http4xxController.php b/core/modules/system/src/Controller/Http4xxController.php
index 0dae4e8..01101af 100644
--- a/core/modules/system/src/Controller/Http4xxController.php
+++ b/core/modules/system/src/Controller/Http4xxController.php
@@ -37,11 +37,12 @@ public function on403() {
       '#markup' => $this->t('You are not authorized to access this page.'),
       '#attached' => array(
         'drupalSettings' => [
-          // 403 page is not marked as an administrative page by
-          // \Drupal::service('router.admin_context')->isAdminRoute() function
-          // in order to use the frontend theme. Since JavaScript relies on a
-          // proper separation of admin pages, it needs to know this is an
-          // actual administrative page.
+          // The 403 page is not marked as an administrative page by
+          // \Drupal::service('router.admin_context')->isAdminRoute() in order
+          // to use the frontend theme. Since JavaScript relies on a proper
+          // separation of admin pages, it needs to know this is an
+          // administrative page, in order to prevent the "back to site"
+          // functionality from saving this page as the last non-admin page.
           'path' => ['currentPathIsAdmin' => TRUE],
         ],
       ),
@@ -59,11 +60,12 @@ public function on404() {
       '#markup' => $this->t('The requested page could not be found.'),
       '#attached' => array(
         'drupalSettings' => [
-          // 404 page is not marked as an administrative page by
-          // \Drupal::service('router.admin_context')->isAdminRoute() function
-          // in order to use the frontend theme. Since JavaScript relies on a
-          // proper separation of admin pages, it needs to know this is an
-          // actual administrative page.
+          // The 404 page is not marked as an administrative page by
+          // \Drupal::service('router.admin_context')->isAdminRoute() in order
+          // to use the frontend theme. Since JavaScript relies on a proper
+          // separation of admin pages, it needs to know this is an
+          // administrative page, in order to prevent the "back to site"
+          // functionality from saving this page as the last non-admin page.
           'path' => ['currentPathIsAdmin' => TRUE],
         ],
       ),