diff --git a/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
index b52d120..fe4ba4b 100644
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -15,6 +15,7 @@
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\HttpKernel;
 use Drupal\Core\KeyValueStore\KeyValueExpirableFactory;
+use Drupal\Core\Render\Element;
 use Drupal\Core\Routing\UrlGeneratorInterface;
 use Drupal\Core\StringTranslation\TranslationInterface;
 use Symfony\Component\EventDispatcher\EventDispatcherInterface;
@@ -992,7 +993,7 @@ public function redirectForm($form_state) {
    */
   protected function doValidateForm(&$elements, &$form_state, $form_id = NULL) {
     // Recurse through all children.
-    foreach ($this->elementChildren($elements) as $key) {
+    foreach (Element::children($elements) as $key) {
       if (isset($elements[$key]) && $elements[$key]) {
         $this->doValidateForm($elements[$key], $form_state);
       }
@@ -1151,7 +1152,7 @@ protected function doValidateForm(&$elements, &$form_state, $form_id = NULL) {
    */
   protected function setElementErrorsFromFormState(array &$elements, array &$form_state) {
     // Recurse through all children.
-    foreach ($this->elementChildren($elements) as $key) {
+    foreach (Element::children($elements) as $key) {
       if (isset($elements[$key]) && $elements[$key]) {
         $this->setElementErrorsFromFormState($elements[$key], $form_state);
       }
@@ -1356,7 +1357,7 @@ public function doBuildForm($form_id, &$element, &$form_state) {
 
     // Recurse through all child elements.
     $count = 0;
-    foreach ($this->elementChildren($element) as $key) {
+    foreach (Element::children($element) as $key) {
       // Prior to checking properties of child elements, their default
       // properties need to be loaded.
       if (isset($element[$key]['#type']) && empty($element[$key]['#defaults_loaded']) && ($info = $this->getElementInfo($element[$key]['#type']))) {
@@ -1762,15 +1763,6 @@ protected function drupalSetMessage($message = NULL, $type = 'status', $repeat =
   }
 
   /**
-   * Wraps element_children().
-   *
-   * @return array
-   */
-  protected function elementChildren(&$elements, $sort = FALSE) {
-    return element_children($elements, $sort);
-  }
-
-  /**
    * Wraps drupal_html_class().
    *
    * @return string
diff --git a/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php b/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
index 2374046..f9a6718 100644
--- a/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
+++ b/core/tests/Drupal/Tests/Core/Form/FormBuilderTest.php
@@ -816,21 +816,6 @@ protected function watchdog($type, $message, array $variables = NULL, $severity
   /**
    * {@inheritdoc}
    */
-  protected function elementChildren(&$elements, $sort = FALSE) {
-    $children = array();
-    foreach ($elements as $key => $value) {
-      if ($key === '' || $key[0] !== '#') {
-        if (is_array($value)) {
-          $children[] = $key;
-        }
-      }
-    }
-    return $children;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   protected function drupalHtmlClass($class) {
     return $class;
   }
diff --git a/core/tests/Drupal/Tests/Core/Render/ElementTest.php b/core/tests/Drupal/Tests/Core/Render/ElementTest.php
index 7d6e1bc..3857826 100644
--- a/core/tests/Drupal/Tests/Core/Render/ElementTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/ElementTest.php
@@ -104,6 +104,29 @@ public function testChildren() {
   }
 
   /**
+   * Tests the children() method with an invalid key.
+   *
+   * @expectedException \PHPUnit_Framework_Error
+   * @expectedExceptionMessage "foo" is an invalid render array key
+   */
+  public function testInvalidChildren() {
+    $element = array(
+      'foo' => 'bar',
+    );
+    Element::children($element);
+  }
+
+  /**
+   * Tests the children() method with an ignored key/value pair.
+   */
+  public function testIgnoredChildren() {
+    $element = array(
+      'foo' => NULL,
+    );
+    $this->assertSame(array(), Element::children($element));
+  }
+
+  /**
    * Tests the visibleChildren() method.
    *
    * @param array $element