diff --git a/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php b/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php
index 7c561e3b19b..3919c09d4f7 100644
--- a/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php
+++ b/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php
@@ -87,7 +87,7 @@ public function __construct(ContainerInterface $container, array $listeners = []
    * {@inheritdoc}
    */
   public function dispatch(object $event, string $event_name = NULL): object {
-    $event_name = is_string($event_name) ?? get_class($event);
+    $event_name = is_string($event_name) ? $event_name : get_class($event);
     if (isset($this->listeners[$event_name])) {
       // Sort listeners if necessary.
       if (isset($this->unsorted[$event_name])) {