diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 5fd1827..db6ecc1 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -293,9 +293,6 @@ function system_element_info() {
     '#group_callback' => 'drupal_group_js',
     '#aggregate_callback' => 'drupal_aggregate_js',
   );
-  $types['mark'] = array(
-    '#theme' => 'mark',
-  );
 
   // Input elements.
   $types['submit'] = array(