diff --git a/core/includes/form.inc b/core/includes/form.inc
index c605237..8bcc8aa 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -1940,7 +1940,7 @@ function form_builder($form_id, &$element, &$form_state) {
   // after normal input parsing has been completed.
   if (isset($element['#after_build']) && !isset($element['#after_build_done'])) {
     foreach ($element['#after_build'] as $callable) {
-      $element = call_user_func_array($callable, array($element, $form_state));
+      $element = call_user_func_array($callable, array($element, &$form_state));
     }
     $element['#after_build_done'] = TRUE;
   }
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index ec4276b..bfeb61d 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -282,8 +282,8 @@ function hook_queue_info_alter(&$queues) {
  *  - "#validate": array of callback functions taking $form and $form_state.
  *  - "#element_validate": array of callback functions taking $element and
  *    $form_state.
- *  - "#pre_render": array of callables taking $element and $form_state.
- *  - "#post_render": array of callback functions taking $element and $form_state.
+ *  - "#pre_render": array of callables taking $element.
+ *  - "#post_render": array of callback functions taking $children and $element.
  *  - "#submit": array of callback functions taking $form and $form_state.
  *  - "#title_display": optional string indicating if and how #title should be
  *    displayed, see theme_form_element() and theme_form_element_label().