diff --git a/core/lib/Drupal/Core/Messenger/Messenger.php b/core/lib/Drupal/Core/Messenger/Messenger.php
index e0707304ad..f94ace9903 100644
--- a/core/lib/Drupal/Core/Messenger/Messenger.php
+++ b/core/lib/Drupal/Core/Messenger/Messenger.php
@@ -43,6 +43,10 @@ public function addMessage($message, $type = self::TYPE_STATUS, $repeat = FALSE)
     if ($repeat || !in_array($message, $this->flashBag->peek($type))) {
       $this->flashBag->add($type, $message);
     }
+
+    // Mark this page as being uncacheable.
+    \Drupal::service('page_cache_kill_switch')->trigger();
+
     return $this;
   }