diff --git a/core/includes/form.inc b/core/includes/form.inc
index c94bc62..2caba0e 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -4376,31 +4376,60 @@ function theme_form_element($variables) {
   }
   $output = '<div' . drupal_attributes($attributes) . '>' . "\n";
 
+  // Composite elements consist of more than one HTML form control. These must
+  // be grouped by a fieldset.
+  $composite = FALSE;
+  if (isset($element['#composite']) && $element['#composite'] === TRUE) {
+    $composite = TRUE;
+  }
+
+  if ($composite) {
+    $output .= '<fieldset>';
+  }
+
   // If #title is not set, we don't display any label or required marker.
   if (!isset($element['#title'])) {
     $element['#title_display'] = 'none';
   }
   $prefix = isset($element['#field_prefix']) ? '<span class="field-prefix">' . $element['#field_prefix'] . '</span> ' : '';
   $suffix = isset($element['#field_suffix']) ? ' <span class="field-suffix">' . $element['#field_suffix'] . '</span>' : '';
+  $children = ' ' . $prefix . $element['#children'] . $suffix;
+
+  // Generate the title, either a legend or a label, only if the title will be
+  // used.
+  if (!in_array($element['#title_display'], array('none', 'attribute'))) {
+    if ($composite) {
+      $attributes = array();
+      if ($element['#title_display'] === 'invisible') {
+        $attributes['class'] = 'element-invisible';
+      }
+      $title = '<legend' . drupal_attributes($attributes) . '>' . $element['#title'];
+      if (!empty($element['#required'])) {
+        $title .= theme('form_required_marker', array('element' => $element));
+      }
+      $title .= '</legend>';
+    } else {
+      $title = ' ' . theme('form_element_label', $variables);
+    }
+  }
 
   switch ($element['#title_display']) {
     case 'before':
     case 'invisible':
-      $output .= ' ' . theme('form_element_label', $variables);
-      $output .= ' ' . $prefix . $element['#children'] . $suffix . "\n";
+      $output .= $title . $children;
       break;
 
     case 'after':
-      $output .= ' ' . $prefix . $element['#children'] . $suffix;
-      $output .= ' ' . theme('form_element_label', $variables) . "\n";
+      $output .= $children . $title;
       break;
 
     case 'none':
     case 'attribute':
       // Output no label and no required marker, only the children.
-      $output .= ' ' . $prefix . $element['#children'] . $suffix . "\n";
+      $output .= $children;
       break;
   }
+  $output .= "\n";
 
   if (!empty($element['#description'])) {
     $attributes = array('class' => 'description');
@@ -4410,6 +4439,10 @@ function theme_form_element($variables) {
     $output .= '<div' . drupal_attributes($attributes) . '>' . $element['#description'] . "</div>\n";
   }
 
+  if ($composite) {
+    $output .= '</fieldset>';
+  }
+
   $output .= "</div>\n";
 
   return $output;
diff --git a/core/modules/system/lib/Drupal/system/Tests/Form/FormTest.php b/core/modules/system/lib/Drupal/system/Tests/Form/FormTest.php
index 20d1f56..f5e260f 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Form/FormTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Form/FormTest.php
@@ -88,7 +88,7 @@ class FormTest extends WebTestBase {
     $elements['file']['empty_values'] = $empty_strings;
 
     // Regular expression to find the expected marker on required elements.
-    $required_marker_preg = '@<label.*<abbr class="form-required" title="This field is required\.">\*</abbr></label>@';
+    $required_marker_preg = '@<(label|legend).*<abbr class="form-required" title="This field is required\.">\*</abbr></\1>@';
 
     // Go through all the elements and all the empty values for them.
     foreach ($elements as $type => $data) {
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 73236f7..d10a1de 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -455,6 +455,7 @@ function system_element_info() {
     '#theme_wrappers' => array('form_element'),
   );
   $types['radios'] = array(
+    '#composite' => TRUE,
     '#input' => TRUE,
     '#process' => array('form_process_radios'),
     '#theme_wrappers' => array('radios'),
@@ -469,6 +470,7 @@ function system_element_info() {
     '#title_display' => 'after',
   );
   $types['checkboxes'] = array(
+    '#composite' => TRUE,
     '#input' => TRUE,
     '#process' => array('form_process_checkboxes'),
     '#theme_wrappers' => array('checkboxes'),
@@ -496,6 +498,7 @@ function system_element_info() {
     '#process' => array('form_process_weight', 'ajax_process_form'),
   );
   $types['date'] = array(
+    '#composite' => TRUE,
     '#input' => TRUE,
     '#element_validate' => array('date_validate'),
     '#process' => array('form_process_date'),