diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 8feb47b..b17e8b3 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1370,7 +1370,12 @@ function system_sort_modules_by_info_name($a, $b) {
 }
 
 /**
- * Array sorting callback; sorts modules or themes by their name.
+ * Array sorting callback; sorts themes by their name.
+ *
+ * Callback for uasort() within
+ * \Drupal\system\Controller\SystemController::themesPage().
+ *
+ * @see system_sort_modules_by_info_name().
  */
 function system_sort_themes($a, $b) {
   if ($a->is_default) {