diff --git a/core/.eslintrc.json b/core/.eslintrc.json
index a2faf64523..d3ae965289 100644
--- a/core/.eslintrc.json
+++ b/core/.eslintrc.json
@@ -10,6 +10,9 @@
     "es6": true,
     "node": true
   },
+  "parserOptions": {
+    "ecmaVersion": 2020
+  },
   "globals": {
     "Drupal": true,
     "drupalSettings": true,
diff --git a/core/themes/olivero/js/messages.js b/core/themes/olivero/js/messages.js
index 942e7ca408..13d9009116 100644
--- a/core/themes/olivero/js/messages.js
+++ b/core/themes/olivero/js/messages.js
@@ -11,6 +11,8 @@
    *   The message object.
    */
   const closeMessage = (message) => {
+    document.querySelector('body')?.classList.add('test-optional-chaining');
+
     const messageContainer = message.querySelector(
       '[data-drupal-selector="messages-container"]',
     );