diff --git a/core/modules/system/lib/Drupal/system/Tests/Entity/FieldAccessTest.php b/core/modules/system/lib/Drupal/system/Tests/Entity/FieldAccessTest.php
index fdcd244..7945b7c 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Entity/FieldAccessTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Entity/FieldAccessTest.php
@@ -22,8 +22,10 @@ class FieldAccessTest extends DrupalUnitTestBase {
   public static $modules = array('entity_test', 'field', 'field_sql_storage', 'system', 'text', 'user');
 
   /**
-   * Holds the currently active global user ID that gets replaced during the
-   * test.
+   * Holds the currently active global user ID that initiated the test run.
+   *
+   * The user ID gets replaced during the test and needs to be kept here so that
+   * it can be restored at the end of the test run.
    *
    * @var int
    */
@@ -43,6 +45,7 @@ protected function setUp() {
     $this->installSchema('field', array('field_config', 'field_config_instance'));
     // Register entity_test text field.
     entity_test_install();
+    // The global user account refers to the user that initiated this test run.
     // Mask the global user as anonymous to avoid any user account loading.
     global $user;
     $this->activeUid = $user->uid;