diff --git a/core/modules/system/lib/Drupal/system/Plugin/Block/SystemHelpBlock.php b/core/modules/system/lib/Drupal/system/Plugin/Block/SystemHelpBlock.php
index 994bf2b..c9b00a7 100644
--- a/core/modules/system/lib/Drupal/system/Plugin/Block/SystemHelpBlock.php
+++ b/core/modules/system/lib/Drupal/system/Plugin/Block/SystemHelpBlock.php
@@ -11,8 +11,10 @@
 use Drupal\Core\Extension\ModuleHandlerInterface;
 use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
 use Drupal\Core\Session\AccountInterface;
+use Symfony\Component\Debug\Exception\FlattenException;
 use Symfony\Component\DependencyInjection\ContainerInterface;
 use Symfony\Component\HttpFoundation\Request;
+use Symfony\Component\HttpFoundation\Response;
 
 /**
  * Provides a 'System Help' block.
@@ -79,7 +81,7 @@ public static function create(ContainerInterface $container, array $configuratio
    */
   public function access(AccountInterface $account) {
     $exception = $this->request->attributes->get('exception');
-    if ($exception && in_array($exception->getStatusCode(), array(403, 404))) {
+    if ($exception instanceof FlattenException && $exception->getStatusCode() >= Response::HTTP_BAD_REQUEST) {
       return FALSE;
     }
     $this->help = $this->getActiveHelp($this->request);
@@ -97,8 +99,8 @@ protected function getActiveHelp(Request $request) {
 
     $arg = drupal_help_arg(explode('/', $request->attributes->get('_system_path')));
 
+    $router_path = trim($request->getPathInfo(), '/');
     foreach ($this->moduleHandler->getImplementations('help') as $module) {
-      $router_path = trim($request->getPathInfo(), '/');
       $function = $module . '_help';
       // Lookup help for this path.
       if ($help = $function($router_path, $arg)) {