only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/StreamWrapper/PublicStream.php
+++ b/core/lib/Drupal/Core/StreamWrapper/PublicStream.php
@@ -8,7 +8,9 @@
 namespace Drupal\Core\StreamWrapper;
 
 use Drupal\Component\Utility\UrlHelper;
+use Drupal\Core\DrupalKernel;
 use Drupal\Core\Site\Settings;
+use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Defines a Drupal public (public://) stream wrapper class.
@@ -61,7 +63,7 @@ public function getExternalUrl() {
    *   The base path for public:// typically sites/default/files.
    */
   public static function basePath() {
-    $base_path = Settings::get('file_public_path', conf_path() . '/files');
+    $base_path = Settings::get('file_public_path', DrupalKernel::findSitePath(Request::createFromGlobals()) . '/files');
     return $base_path;
   }