diff --git a/core/lib/Drupal/Core/Messenger/BaseMessenger.php b/core/lib/Drupal/Core/Messenger/BaseMessenger.php
index ce45ebf3af..f76c295301 100644
--- a/core/lib/Drupal/Core/Messenger/BaseMessenger.php
+++ b/core/lib/Drupal/Core/Messenger/BaseMessenger.php
@@ -7,6 +7,8 @@
 
 /**
  * Provides a base Messenger implementation.
+ *
+ * @internal
  */
 abstract class BaseMessenger implements MessengerInterface {
 
diff --git a/core/lib/Drupal/Core/Messenger/ChainedMessenger.php b/core/lib/Drupal/Core/Messenger/ChainedMessenger.php
index e69f8472e9..21b39b691b 100644
--- a/core/lib/Drupal/Core/Messenger/ChainedMessenger.php
+++ b/core/lib/Drupal/Core/Messenger/ChainedMessenger.php
@@ -8,6 +8,8 @@
  * This implementation uses a memory messenger for handling messages before the
  * container is initialized. When initialised, it will copy over messages and
  * use that thereafter.
+ *
+ * @internal
  */
 class ChainedMessenger extends BaseMessenger {
 
diff --git a/core/lib/Drupal/Core/Messenger/MemoryMessenger.php b/core/lib/Drupal/Core/Messenger/MemoryMessenger.php
index be97620acf..e82c78e21a 100644
--- a/core/lib/Drupal/Core/Messenger/MemoryMessenger.php
+++ b/core/lib/Drupal/Core/Messenger/MemoryMessenger.php
@@ -2,13 +2,12 @@
 
 namespace Drupal\Core\Messenger;
 
-use Drupal\Component\Render\MarkupInterface;
-use Drupal\Core\Render\Markup;
-
 /**
  * Provides a Messenger implementation which stores messages in memory.
  *
  * Used for early the bootstrap phase when there is no service container.
+ *
+ * @internal
  */
 class MemoryMessenger extends BaseMessenger {