diff --git a/core/includes/form.inc b/core/includes/form.inc
index 4689711..4fe6607 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -2885,7 +2885,7 @@ function form_get_options($element, $key) {
  *   An associative array containing:
  *   - element: An associative array containing the properties of the element.
  *     Properties used: #attributes, #children, #collapsed, #description, #id,
- *     #title, #value.
+ *     #title, #title_display.
  *
  * @ingroup themeable
  */
@@ -2916,9 +2916,7 @@ function theme_fieldset($variables) {
 
   }
   $output .= $element['#children'];
-  if (isset($element['#value'])) {
-    $output .= $element['#value'];
-  }
+
   $output .= '</div>';
   $output .= "</fieldset>\n";
   return $output;
@@ -3197,11 +3195,15 @@ function theme_checkboxes($variables) {
 }
 
 /**
- * Adds form element theming to an element if its title or description is set.
+ * Adds theming to composite form elements such as checkboxes and radios.
  *
- * This is used as a pre render function for checkboxes and radios.
+ * If either the title or description is set for the composite element as a * whole, then this adds either a 'fieldset' or 'form_element' theme wrapper to
+ * render them. A fieldset is generally preferred to assist screen readers
+ * (http://webaim.org/techniques/forms/screen_reader#group), but is not used
+ * when #title_display is set to an option impossible to render as a fieldset
+ * legend.
  */
-function form_pre_render_conditional_form_element($element) {
+function form_pre_render_composite_form_element($element) {
   // Set the element's title attribute to show #title as a tooltip, if needed.
   if (isset($element['#title']) && $element['#title_display'] == 'attribute') {
     $element['#attributes']['title'] = $element['#title'];
@@ -3212,7 +3214,16 @@ function form_pre_render_conditional_form_element($element) {
   }
 
   if (isset($element['#title']) || isset($element['#description'])) {
-    $element['#theme_wrappers'][] = 'form_element';
+    // To assist screen readers, use a fieldset wrapper when possible, but
+    // fieldset legends are only compatible with the 'before' and 'invisible'
+    // options for #title_display.
+    if (!isset($element['#title_display']) || in_array($element['#title_display'], array('before', 'invisible'))) {
+      $wrapper = 'fieldset';
+    }
+    else {
+      $wrapper = 'form_element';
+    }
+    $element['#theme_wrappers'][] = $wrapper;
   }
   return $element;
 }
@@ -4681,7 +4692,7 @@ function form_process_file($element) {
  *   property hides the label for everyone except screen readers.
  * - attribute: Set the title attribute on the element to create a tooltip
  *   but output no label element. This is supported only for checkboxes
- *   and radios in form_pre_render_conditional_form_element(). It is used
+ *   and radios in form_pre_render_composite_form_element(). It is used
  *   where a visual label is not needed, such as a table of checkboxes where
  *   the row and column provide the context. The tooltip will include the
  *   title and required marker.
diff --git a/core/modules/system/css/system.theme.css b/core/modules/system/css/system.theme.css
index 19bb45f..9d972ed 100644
--- a/core/modules/system/css/system.theme.css
+++ b/core/modules/system/css/system.theme.css
@@ -7,7 +7,7 @@
  * HTML elements.
  */
 fieldset {
-  border: 1px solid #ccc;
+  border: 0;
   margin: 1em 0;
   padding: 0.5em;
 }
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 f402395..eca06a9 100644
--- a/core/modules/system/lib/Drupal/system/Tests/Form/FormTest.php
+++ b/core/modules/system/lib/Drupal/system/Tests/Form/FormTest.php
@@ -94,7 +94,7 @@ function testRequiredFields() {
     $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 ae4131d..4babeba 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -448,7 +448,7 @@ function system_element_info() {
     '#input' => TRUE,
     '#process' => array('form_process_radios'),
     '#theme_wrappers' => array('radios'),
-    '#pre_render' => array('form_pre_render_conditional_form_element'),
+    '#pre_render' => array('form_pre_render_composite_form_element'),
   );
   $types['radio'] = array(
     '#input' => TRUE,
@@ -462,7 +462,7 @@ function system_element_info() {
   $types['checkboxes'] = array(
     '#input' => TRUE,
     '#process' => array('form_process_checkboxes'),
-    '#pre_render' => array('form_pre_render_conditional_form_element'),
+    '#pre_render' => array('form_pre_render_composite_form_element'),
     '#theme_wrappers' => array('checkboxes'),
   );
   $types['checkbox'] = array(
diff --git a/core/themes/seven/style.css b/core/themes/seven/style.css
index 86ac064..7cd0b06 100644
--- a/core/themes/seven/style.css
+++ b/core/themes/seven/style.css
@@ -25,6 +25,8 @@ hr {
 summary,
 legend {
   font-weight: bold;
+}
+summary {
   text-transform: uppercase;
 }
 h1,