diff --git a/core/misc/states.js b/core/misc/states.js
index 171bac5..75ee01d 100644
--- a/core/misc/states.js
+++ b/core/misc/states.js
@@ -420,7 +420,7 @@ states.Trigger.states = {
 
   collapsed: {
     'collapsed': function(e) {
-      return (typeof e !== 'undefined' && 'value' in e) ? e.value : this.is('.collapsed');
+      return (typeof e !== 'undefined' && 'value' in e) ? e.value : !this.is('[open]');
     }
   }
 };
@@ -477,6 +477,8 @@ states.State.aliases = {
   'unchecked': '!checked',
   'irrelevant': '!relevant',
   'expanded': '!collapsed',
+  'open': '!collapsed',
+  'closed': 'collapsed',
   'readwrite': '!readonly'
 };
 
@@ -537,7 +539,7 @@ $(document).bind('state:checked', function(e) {
 
 $(document).bind('state:collapsed', function(e) {
   if (e.trigger) {
-    if ($(e.target).is('.collapsed') !== e.value) {
+    if ($(e.target).is('[open]') === e.value) {
       $(e.target).find('> summary a').click();
     }
   }
diff --git a/core/modules/system/tests/modules/design_test/form/details.inc b/core/modules/system/tests/modules/design_test/form/details.inc
index 6d7ac68..febcda3 100644
--- a/core/modules/system/tests/modules/design_test/form/details.inc
+++ b/core/modules/system/tests/modules/design_test/form/details.inc
@@ -15,6 +15,11 @@ function design_test_form_details($form, &$form_state) {
     '#description' => 'Details description',
     '#collapsible' => TRUE,
     '#collapsed' => FALSE,
+    '#states' => array(
+      'collapsed' => array(
+        ':input[name="states-trigger"]' => array('checked' => TRUE),
+      ),
+    ),
   );
 
   $form['collapsed'] = array(
@@ -143,6 +148,26 @@ function design_test_form_details($form, &$form_state) {
   );
   $form['subtabs'][1] += $subform;
 
+
+  // #states supports:
+  // - a 'collapsed' state trigger
+  // - a 'collapsed' remote condition
+  $form['states-trigger'] = array(
+    '#type' => 'checkbox',
+    '#title' => 'Collapse first details',
+    '#weight' => -100,
+  );
+  $form['states-condition'] = array(
+    '#type' => 'checkbox',
+    '#title' => 'Required if second details are collapsed.',
+    '#states' => array(
+      'required' => array(
+        'details#edit-collapsed' => array('collapsed' => TRUE),
+      ),
+    ),
+    '#weight' => -100,
+  );
+
   return $form;
 }