diff --git a/core/includes/common.inc b/core/includes/common.inc
index 4668a90..2e0e5a3 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -5216,8 +5216,8 @@ function drupal_render(&$elements) {
   // that the $element or the children can be altered or corrected before the
   // element is rendered into the final text.
   if (isset($elements['#pre_render'])) {
-    foreach ($elements['#pre_render'] as $function) {
-      $elements = $function($elements);
+    foreach ($elements['#pre_render'] as $callable) {
+      $elements = call_user_func($callable, $elements);
     }
   }
 
@@ -5284,8 +5284,8 @@ function drupal_render(&$elements) {
   // content is sent to the browser. The changes are made on $content
   // which allows the output'ed text to be filtered.
   if (isset($elements['#post_render'])) {
-    foreach ($elements['#post_render'] as $function) {
-      $elements['#children'] = $function($elements['#children'], $elements);
+    foreach ($elements['#post_render'] as $callable) {
+      $elements['#children'] = call_user_func($callable, $elements['#children'], $elements);
     }
   }
 
diff --git a/core/includes/form.inc b/core/includes/form.inc
index 2f930e2..8bcc8aa 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -1750,7 +1750,7 @@ function form_error(&$element, $message = '') {
  *   adds the attributes and JavaScript needed to make the details work in older
  *   browsers. The #process functions are called in preorder traversal, meaning
  *   they are called for the parent element first, then for the child elements.
- * - $element['#after_build']: An array of functions called after form_builder()
+ * - $element['#after_build']: An array of callables called after form_builder()
  *   is done with its processing of the element. These are called in postorder
  *   traversal, meaning they are called for the child elements first, then for
  *   the parent element.
@@ -1939,8 +1939,8 @@ function form_builder($form_id, &$element, &$form_state) {
   // The #after_build flag allows any piece of a form to be altered
   // after normal input parsing has been completed.
   if (isset($element['#after_build']) && !isset($element['#after_build_done'])) {
-    foreach ($element['#after_build'] as $function) {
-      $element = $function($element, $form_state);
+    foreach ($element['#after_build'] as $callable) {
+      $element = call_user_func_array($callable, array($element, &$form_state));
     }
     $element['#after_build_done'] = TRUE;
   }
diff --git a/core/modules/system/system.api.php b/core/modules/system/system.api.php
index 5360a83..bfeb61d 100644
--- a/core/modules/system/system.api.php
+++ b/core/modules/system/system.api.php
@@ -282,8 +282,8 @@ function hook_queue_info_alter(&$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 callback functions 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().