diff --git a/core/misc/collapse.js b/core/misc/collapse.js
index 767325e..4d408f2 100644
--- a/core/misc/collapse.js
+++ b/core/misc/collapse.js
@@ -21,6 +21,7 @@
     // Expand details if there are errors inside, or if it contains an
     // element that is targeted by the URI fragment identifier.
     var anchor = location.hash && location.hash !== '#' ? ', ' + location.hash : '';
+
     if (this.$node.find('.error' + anchor).length) {
       this.$node.attr('open', true);
     }
@@ -140,6 +141,32 @@
     }
   };
 
+  /**
+   * Set all hash links that target details to expand them.
+   *
+   * @type {Drupal~behavior}
+   *
+   * @prop {Drupal~behaviorAttach} attach
+   *   Attaches behavior for the details element.
+   */
+  Drupal.behaviors.watchHashLinks = {
+    attach: function (context) {
+      $(context).on('click', $('a[href^="#"]').not('.vertical-tabs__menu-item.is-selected a'), function(event) {
+        var $item = $(event.target.hash);
+
+        if (event.target.hash != '#' && $item.length) {
+          $item.parents('details').attr('open', true).find('> summary').attr({
+            'aria-expanded': true,
+            'aria-pressed': true
+          });
+          $item.parents('.vertical-tabs__pane').each(function(index, pane) {
+            $(pane).data('verticalTab').focus();
+          });
+        }
+      });
+    }
+  };
+
   // Expose constructor in the public space.
   Drupal.CollapsibleDetails = CollapsibleDetails;