diff --git a/core/modules/system/src/Tests/KeyValueStore/GarbageCollectionTest.php b/core/modules/system/src/Tests/KeyValueStore/GarbageCollectionTest.php
index 7fbb265..6b46b7c 100644
--- a/core/modules/system/src/Tests/KeyValueStore/GarbageCollectionTest.php
+++ b/core/modules/system/src/Tests/KeyValueStore/GarbageCollectionTest.php
@@ -29,7 +29,7 @@ class GarbageCollectionTest extends KernelTestBase {
   protected function setUp() {
     parent::setUp();
 
-    // The additional tables are necessary due to the call to system_cron().
+    // These additional tables are necessary due to the call to system_cron().
     $this->installSchema('system', array('key_value_expire', 'flood', 'queue'));
   }
 
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index c95fc3c..dbbfd45 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1143,22 +1143,22 @@ function system_get_module_admin_tasks($module, array $info) {
 /**
  * Implements hook_cron().
  *
- * Remove older rows from flood and batch table. Remove old temporary files.
+ * Remove older rows from flood, batch cache and expirable keyvalue tables.
  */
 function system_cron() {
-  // Cleanup the flood.
+  // Clean up the flood.
   \Drupal::flood()->garbageCollection();
 
   foreach (Cache::getBins() as $cache_backend) {
     $cache_backend->garbageCollection();
   }
 
-  // Cleanup the expirable key value database store.
+  // Clean up the expirable key value database store.
   if (\Drupal::service('keyvalue.expirable.database') instanceof KeyValueDatabaseExpirableFactory) {
     \Drupal::service('keyvalue.expirable.database')->garbageCollection();
   }
 
-  // Cleanup the queue for failed batches.
+  // Clean up the queue for failed batches.
   db_delete('queue')
     ->condition('created', REQUEST_TIME - 864000, '<')
     ->condition('name', 'drupal_batch:%', 'LIKE')