diff --git a/core/modules/system/src/Tests/Theme/MessageTest.php b/core/modules/system/src/Tests/Theme/MessageTest.php
index 09ee33f..2fbe200 100644
--- a/core/modules/system/src/Tests/Theme/MessageTest.php
+++ b/core/modules/system/src/Tests/Theme/MessageTest.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Definition of Drupal\system\Tests\Theme\MessageTest.
+ * Contains Drupal\system\Tests\Theme\MessageTest.
  */
 
 namespace Drupal\system\Tests\Theme;
@@ -17,9 +17,7 @@
 class MessageTest extends KernelTestBase {
 
   /**
-   * Modules to enable.
-   *
-   * @var array
+   * {@inheritdoc}
    */
   public static $modules = array('system');
 
diff --git a/core/modules/system/templates/status-messages.html.twig b/core/modules/system/templates/status-messages.html.twig
index 0e10fa8..063e6c4 100644
--- a/core/modules/system/templates/status-messages.html.twig
+++ b/core/modules/system/templates/status-messages.html.twig
@@ -17,6 +17,8 @@
  * - status_headings: List of all status types.
  * - display: (optional) May have a value of 'status' or 'error' when only
  *   displaying messages of that specific type.
+ * - attributes: HTML attributes for the element, including:
+ *   - class: HTML classes.
  *
  * @see template_preprocess_status_messages()
  *
@@ -50,5 +52,6 @@
       </div>
     {% endif %}
   </div>
+  {# Remove type specific classes. #}
   {{ attributes.removeClass(classes) }}
 {% endfor %}