diff --git a/core/includes/common.inc b/core/includes/common.inc
index 0c16ac9..133863f 100644
--- a/core/includes/common.inc
+++ b/core/includes/common.inc
@@ -3711,6 +3711,14 @@ function drupal_add_js($data = NULL, $options = NULL) {
             'pathPrefix' => $pathPrefix,
             'currentPath' => current_path(),
           );
+          // Expose errors in Drupal behaviors, unless error reporting is
+          // disabled.
+          $error_level = config('system.logging')->get('error_level');
+          if (!empty($error_level) && $error_level != 'hide') {
+            $javascript['settings']['data'][] = array(
+              'errors' => 1,
+            );
+          }
         }
         // All JavaScript settings are placed in the header of the page with
         // the library weight so that inline scripts appear afterwards.
diff --git a/core/misc/drupal.js b/core/misc/drupal.js
index 627e264..eb034c0 100644
--- a/core/misc/drupal.js
+++ b/core/misc/drupal.js
@@ -79,6 +79,11 @@ Drupal.attachBehaviors = function (context, settings) {
   // Execute all of them.
   for (i in behaviors) {
     if (behaviors.hasOwnProperty(i) && typeof behaviors[i].attach === 'function') {
+      // If errors are not hidden, execute behaviors directly.
+      if (settings.errors) {
+        behaviors[i].attach(context, settings);
+        continue;
+      }
       // Don't stop the execution of behaviors in case of an error.
       try {
         behaviors[i].attach(context, settings);
@@ -142,6 +147,11 @@ Drupal.detachBehaviors = function (context, settings, trigger) {
   // Execute all of them.
   for (i in behaviors) {
     if (behaviors.hasOwnProperty(i) && typeof behaviors[i].detach === 'function' ) {
+      // If errors are not hidden, execute behaviors directly.
+      if (settings.errors) {
+        behaviors[i].detach(context, settings, trigger);
+        continue;
+      }
       // Don't stop the execution of behaviors in case of an error.
       try {
         behaviors[i].detach(context, settings, trigger);
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 17015c6..dbf1fd8 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -1220,6 +1220,7 @@ function system_library_info() {
     ),
     'dependencies' => array(
       array('system', 'jquery'),
+      array('system', 'drupalSettings'),
     ),
   );