diff --git a/core/modules/node/lib/Drupal/node/NodeBreadcrumbBuilder.php b/core/modules/node/lib/Drupal/node/NodeBreadcrumbBuilder.php
index 65cc3de..5e964b4 100644
--- a/core/modules/node/lib/Drupal/node/NodeBreadcrumbBuilder.php
+++ b/core/modules/node/lib/Drupal/node/NodeBreadcrumbBuilder.php
@@ -34,7 +34,7 @@ public function build(array $attributes) {
 
     // @todo This only works for legacy routes. Once node/% has been converted
     //   to the new router this code will need to be updated.
-    if (isset($attributes['_drupal_menu_item'])) {
+    if (isset($attributes['_drupal_menu_item']) && isset($attributes['node'])) {
       $trail = explode('/', $attributes['_drupal_menu_item']['href']);
       $node = $attributes['_drupal_menu_item']['map'][1];
     }