diff --git a/core/lib/Drupal/Core/EventSubscriber/AcceptNegotiation406.php b/core/lib/Drupal/Core/EventSubscriber/AcceptNegotiation406.php
index 4bfc942..72683e1 100644
--- a/core/lib/Drupal/Core/EventSubscriber/AcceptNegotiation406.php
+++ b/core/lib/Drupal/Core/EventSubscriber/AcceptNegotiation406.php
@@ -26,7 +26,7 @@ class AcceptNegotiation406 implements EventSubscriberInterface {
    * @param \Symfony\Component\HttpKernel\Event\GetResponseForControllerResultEvent $event
    *   The event to process.
    */
-  function onViewDetect406(GetResponseForControllerResultEvent $event) {
+  public function onViewDetect406(GetResponseForControllerResultEvent $event) {
     $request = $event->getRequest();
     $result = $event->getControllerResult();