diff -u b/menu_attributes.module b/menu_attributes.module
--- b/menu_attributes.module
+++ b/menu_attributes.module
@@ -410,12 +410,14 @@
  * Implements hook_theme_registry_alter().
  */
 function menu_attributes_theme_registry_alter(&$registry) {
-  array_unshift($registry['menu_tree']['preprocess functions'], 'menu_attributes_prepreprocess_menu_tree');
-  $registry['menu_tree']['function'] = 'menu_attributes_menu_tree';
+  if ($registry['menu_tree']['function'] == 'theme_menu_tree') {
+    array_unshift($registry['menu_tree']['preprocess functions'], 'menu_attributes_prepreprocess_menu_tree');
+    $registry['menu_tree']['function'] = 'menu_attributes_menu_tree';
+  }
 }
 
 /**
- * Prepares variables for theme_menu_tree().
+ * Implements hook_preproces_menu_tree().
  */
 function menu_attributes_prepreprocess_menu_tree(&$variables) {
   $first_element_key = current(element_children($variables['tree']));