diff --git a/core/includes/form.inc b/core/includes/form.inc
index 375f178671d..68a16cd515b 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -3870,19 +3870,19 @@ function form_validate_machine_name(&$element, &$form_state) {
 }
 
 /**
- * Arranges details into groups.
+ * Arranges elements into groups.
  *
  * @param $element
  *   An associative array containing the properties and children of the
- *   details. Note that $element must be taken by reference here, so processed
+ *   element. Note that $element must be taken by reference here, so processed
  *   child elements are taken over into $form_state.
  * @param $form_state
- *   The $form_state array for the form this details belongs to.
+ *   The $form_state array for the form this element belongs to.
  *
  * @return
  *   The processed element.
  */
-function form_process_details(&$element, &$form_state) {
+function form_process_group(&$element, &$form_state) {
   $parents = implode('][', $element['#parents']);
 
   // Each details element forms a new group. The #type 'vertical_tabs' basically
@@ -3904,14 +3904,14 @@ function form_process_details(&$element, &$form_state) {
 }
 
 /**
- * Adds members of this group as actual elements for rendering.
+ * Adds form element theming to details.
  *
  * @param $element
  *   An associative array containing the properties and children of the
  *   details.
  *
  * @return
- *   The modified element with all group members.
+ *   The modified element.
  */
 function form_pre_render_details($element) {
   // The .form-wrapper class is required for #states to treat details like
@@ -3929,10 +3929,25 @@ function form_pre_render_details($element) {
     $element['#attributes']['open'] = 'open';
   }
 
-  // Details may be rendered outside of a Form API context.
+  return $element;
+}
+
+/**
+ * Adds members of this group as actual elements for rendering.
+ *
+ * @param $element
+ *   An associative array containing the properties and children of the
+ *   element.
+ *
+ * @return
+ *   The modified element with all group members.
+ */
+function form_pre_render_group($element) {
+  // The element may be rendered outside of a Form API context.
   if (!isset($element['#parents']) || !isset($element['#groups'])) {
     return $element;
   }
+
   // Inject group member elements belonging to this group.
   $parents = implode('][', $element['#parents']);
   $children = element_children($element['#groups'][$parents]);
diff --git a/core/modules/system/lib/Drupal/system/Tests/Form/ElementTest.php b/core/modules/system/lib/Drupal/system/Tests/Form/ElementTest.php
index 3b7f935ddf3..e3521ccf6a4 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Form/ElementTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Form/ElementTest.php
@@ -107,4 +107,23 @@ class ElementTest extends WebTestBase {
     $this->assertEqual(1, count($this->xpath('//*[contains(concat(" ", @class, " "), " button-danger ")]')));
   }
 
+  /**
+   * Tests the #group property.
+   */
+  function testGroupElements() {
+    $this->drupalGet('form-test/group-details');
+    $elements = $this->xpath('//div[@class="details-wrapper"]//div[@class="details-wrapper"]//label');
+    $this->assertTrue(count($elements) == 1);
+    $this->drupalGet('form-test/group-container');
+    $elements = $this->xpath('//div[@id="edit-container"]//div[@class="details-wrapper"]//label');
+    $this->assertTrue(count($elements) == 1);
+    $this->drupalGet('form-test/group-fieldset');
+    $elements = $this->xpath('//fieldset[@id="edit-fieldset"]//div[@id="edit-meta"]//label');
+    $this->assertTrue(count($elements) == 1);
+    $this->drupalGet('form-test/group-vertical-tabs');
+    $elements = $this->xpath('//div[@class="vertical-tabs-panes"]//details[@id="edit-meta"]//label');
+    $this->assertTrue(count($elements) == 1);
+    $elements = $this->xpath('//div[@class="vertical-tabs-panes"]//details[@id="edit-meta-2"]//label');
+    $this->assertTrue(count($elements) == 1);
+  }
 }
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 65b19149f2c..336f84b5008 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -543,15 +543,16 @@ function system_element_info() {
   );
   $types['fieldset'] = array(
     '#value' => NULL,
-    '#process' => array('ajax_process_form'),
+    '#process' => array('form_process_group', 'ajax_process_form'),
+    '#pre_render' => array('form_pre_render_group'),
     '#theme_wrappers' => array('fieldset'),
   );
   $types['details'] = array(
     '#collapsible' => FALSE,
     '#collapsed' => FALSE,
     '#value' => NULL,
-    '#process' => array('form_process_details', 'ajax_process_form'),
-    '#pre_render' => array('form_pre_render_details'),
+    '#process' => array('form_process_group', 'ajax_process_form'),
+    '#pre_render' => array('form_pre_render_details', 'form_pre_render_group'),
     '#theme_wrappers' => array('details'),
   );
   $types['vertical_tabs'] = array(
@@ -570,7 +571,8 @@ function system_element_info() {
   );
 
   $types['container'] = array(
-    '#process' => array('form_process_container'),
+    '#process' => array('form_process_group', 'form_process_container'),
+    '#pre_render' => array('form_pre_render_group'),
     '#theme_wrappers' => array('container'),
   );
   $types['actions'] = array(
diff --git a/core/modules/system/tests/modules/form_test/form_test.module b/core/modules/system/tests/modules/form_test/form_test.module
index 9fd4bcb2f81..8e1992ce454 100644
--- a/core/modules/system/tests/modules/form_test/form_test.module
+++ b/core/modules/system/tests/modules/form_test/form_test.module
@@ -314,6 +314,31 @@ function form_test_menu() {
     'access callback' => TRUE,
   );
 
+  $items['form-test/group-details'] = array(
+    'title' => 'Group details testing',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('form_test_group_details'),
+    'access callback' => TRUE,
+  );
+  $items['form-test/group-container'] = array(
+    'title' => 'Group container testing',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('form_test_group_container'),
+    'access callback' => TRUE,
+  );
+  $items['form-test/group-fieldset'] = array(
+    'title' => 'Group fieldset testing',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('form_test_group_fieldset'),
+    'access callback' => TRUE,
+  );
+  $items['form-test/group-vertical-tabs'] = array(
+    'title' => 'Group vertical tabs testing',
+    'page callback' => 'drupal_get_form',
+    'page arguments' => array('form_test_group_vertical_tabs'),
+    'access callback' => TRUE,
+  );
+
   return $items;
 }
 
@@ -2333,3 +2358,90 @@ function form_test_button_class($form, &$form_state) {
   );
   return $form;
 }
+
+/**
+ * Builds a simple form to test the #group property on #type 'details'.
+ */
+function form_test_group_details() {
+  $form['details'] = array(
+    '#type' => 'details',
+    '#title' => 'Root element',
+  );
+  $form['meta'] = array(
+    '#type' => 'details',
+    '#title' => 'Group element',
+    '#group' => 'details',
+  );
+  $form['meta']['element'] = array(
+    '#type' => 'textfield',
+    '#title' => 'Nest in details element',
+  );
+  return $form;
+}
+
+/**
+ * Builds a simple form to test the #group property on #type 'container'.
+ */
+function form_test_group_container() {
+  $form['container'] = array(
+    '#type' => 'container',
+  );
+  $form['meta'] = array(
+    '#type' => 'details',
+    '#title' => 'Group element',
+    '#group' => 'container',
+  );
+  $form['meta']['element'] = array(
+    '#type' => 'textfield',
+    '#title' => 'Nest in details element',
+  );
+  return $form;
+}
+
+/**
+ * Builds a simple form to test the #group property on #type 'fieldset'.
+ */
+function form_test_group_fieldset() {
+  $form['fieldset'] = array(
+    '#type' => 'fieldset',
+    '#title' => 'Fieldset',
+  );
+  $form['meta'] = array(
+    '#type' => 'container',
+    '#title' => 'Group element',
+    '#group' => 'fieldset',
+  );
+  $form['meta']['element'] = array(
+    '#type' => 'textfield',
+    '#title' => 'Nest in container element',
+  );
+  return $form;
+}
+
+/**
+ * Builds a simple form to test the #group property on #type 'vertical_tabs'.
+ */
+function form_test_group_vertical_tabs() {
+  $form['vertical_tabs'] = array(
+    '#type' => 'vertical_tabs',
+  );
+  $form['meta'] = array(
+    '#type' => 'details',
+    '#title' => 'First group element',
+    '#group' => 'vertical_tabs',
+  );
+  $form['meta']['element'] = array(
+    '#type' => 'textfield',
+    '#title' => 'First nested element in details element',
+  );
+  $form['meta_2'] = array(
+    '#type' => 'details',
+    '#title' => 'Second group element',
+    '#group' => 'vertical_tabs',
+  );
+  $form['meta_2']['element_2'] = array(
+    '#type' => 'textfield',
+    '#title' => 'Second nested element in details element',
+  );
+  return $form;
+}