diff --git a/core/modules/system/src/Tests/File/StreamWrapperTest.php b/core/modules/system/src/Tests/File/StreamWrapperTest.php
index 2f460f7..b96f288 100644
--- a/core/modules/system/src/Tests/File/StreamWrapperTest.php
+++ b/core/modules/system/src/Tests/File/StreamWrapperTest.php
@@ -7,8 +7,10 @@
 
 namespace Drupal\system\Tests\File;
 
+use Drupal\Core\DrupalKernel;
 use Drupal\Core\Site\Settings;
 use Drupal\Core\StreamWrapper\PublicStream;
+use Symfony\Component\HttpFoundation\Request;
 
 /**
  * Tests stream wrapper functions.
@@ -38,6 +40,17 @@ class StreamWrapperTest extends FileTestBase {
    */
   protected $classname = 'Drupal\file_test\StreamWrapper\DummyStreamWrapper';
 
+  function setUp() {
+    // Add file_private_path setting.
+    $settings = Settings::getAll();
+    $request = Request::create('/');;
+    $site_path = DrupalKernel::findSitePath($request);
+    $settings['file_private_path'] = $site_path . '/private';
+    new Settings($settings + Settings::getAll());
+
+    parent::setUp();
+  }
+
   /**
    * Test the getClassName() function.
    */