diff --git a/core/lib/Drupal/Core/Menu/MenuLinkTree.php b/core/lib/Drupal/Core/Menu/MenuLinkTree.php
index 518534f..a5ea3d2 100644
--- a/core/lib/Drupal/Core/Menu/MenuLinkTree.php
+++ b/core/lib/Drupal/Core/Menu/MenuLinkTree.php
@@ -255,7 +255,7 @@ protected function buildItems(array $tree, CacheableMetadata &$tree_access_cache
       }
       // Set a helper variable to indicate whether link is in active trail.
       if ($data->inActiveTrail) {
-        $element['is_active_trail'] = TRUE;
+        $element['in_active_trail'] = TRUE;
       }
 
       // Note: links are rendered in the menu.html.twig template; and they
diff --git a/core/modules/system/tests/src/Unit/Menu/MenuLinkTreeTest.php b/core/modules/system/tests/src/Unit/Menu/MenuLinkTreeTest.php
index 6385c69..64d14b9 100644
--- a/core/modules/system/tests/src/Unit/Menu/MenuLinkTreeTest.php
+++ b/core/modules/system/tests/src/Unit/Menu/MenuLinkTreeTest.php
@@ -155,8 +155,8 @@ public function providerTestBuildCacheability() {
       elseif ($element->hasChildren) {
         $return['is_collapsed'] = TRUE;
       }
-      if ($ekement->inActiveTrail) {
-        $return['is_active_trail'] = TRUE;
+      if ($element->inActiveTrail) {
+        $return['in_active_trail'] = TRUE;
       }
 
       return $return;
diff --git a/core/modules/toolbar/templates/menu--toolbar.html.twig b/core/modules/toolbar/templates/menu--toolbar.html.twig
index 090b7a4..4165072 100644
--- a/core/modules/toolbar/templates/menu--toolbar.html.twig
+++ b/core/modules/toolbar/templates/menu--toolbar.html.twig
@@ -33,14 +33,14 @@
     {% endif %}
       {% for item in items %}
       {%
-        set class = [
+        set classes = [
           'menu-item',
           item.is_expanded ? 'menu-item--expanded',
           item.is_collapsed ? 'menu-item--collapsed',
-          item.is_active_trail ? 'menu-item--active-trail',
+          item.in_active_trail ? 'menu-item--active-trail',
         ]
       %}
-        <li{{ item.attributes.addClass(class) }}>
+        <li{{ item.attributes.addClass(classes) }}>
           {{ link(item.title, item.url) }}
           {% if item.below %}
             {{ menus.menu_links(item.below, attributes, menu_level + 1) }}
diff --git a/core/themes/classy/templates/navigation/menu.html.twig b/core/themes/classy/templates/navigation/menu.html.twig
index bd43a9b..3ebed26 100644
--- a/core/themes/classy/templates/navigation/menu.html.twig
+++ b/core/themes/classy/templates/navigation/menu.html.twig
@@ -31,14 +31,14 @@
     {% endif %}
     {% for item in items %}
       {%
-        set class = [
+        set classes = [
           'menu-item',
           item.is_expanded ? 'menu-item--expanded',
           item.is_collapsed ? 'menu-item--collapsed',
-          item.is_active_trail ? 'menu-item--active-trail',
+          item.in_active_trail ? 'menu-item--active-trail',
         ]
       %}
-      <li{{ item.attributes.addClass(class) }}>
+      <li{{ item.attributes.addClass(classes) }}>
         {{ link(item.title, item.url) }}
         {% if item.below %}
           {{ menus.menu_links(item.below, attributes, menu_level + 1) }}