diff --git modules/file/file.module modules/file/file.module
index f61c159..bf09e8f 100644
--- modules/file/file.module
+++ modules/file/file.module
@@ -349,7 +349,7 @@ function file_managed_file_process($element, &$form_state, $form) {
   $element['#tree'] = TRUE;
 
   $ajax_settings = array(
-    'path' => 'file/ajax/' . implode('/', $element['#parents']) . '/' . $form['form_build_id']['#value'],
+    'path' => 'file/ajax/' . implode('/', $element['#array_parents']) . '/' . $form['form_build_id']['#value'],
     'wrapper' => $element['#id'] . '-ajax-wrapper',
     'method' => 'replace',
     'effect' => 'fade',