.../big_pipe/src/Controller/BigPipeController.php  |  2 +-
 core/modules/big_pipe/src/Render/BigPipe.php       |  4 ++--
 core/modules/big_pipe/src/Render/BigPipeMarkup.php | 28 ++++++++++++++++++++++
 .../src/Tests/BigPipePlaceholderTestCases.php      |  6 ++---
 .../big_pipe_test/src/BigPipeTestController.php    |  4 ++--
 5 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/core/modules/big_pipe/src/Controller/BigPipeController.php b/core/modules/big_pipe/src/Controller/BigPipeController.php
index 6139f46..282a634 100644
--- a/core/modules/big_pipe/src/Controller/BigPipeController.php
+++ b/core/modules/big_pipe/src/Controller/BigPipeController.php
@@ -52,7 +52,7 @@ public function setNoJsCookie(Request $request) {
     }
 
     if (!$request->query->has('destination')) {
-      throw new HttpException(500, 'The original location is missing.');
+      throw new HttpException(400, 'The original location is missing.');
     }
 
     $response = new LocalRedirectResponse($request->query->get('destination'));
diff --git a/core/modules/big_pipe/src/Render/BigPipe.php b/core/modules/big_pipe/src/Render/BigPipe.php
index 1c00f1e..9af1b0f 100644
--- a/core/modules/big_pipe/src/Render/BigPipe.php
+++ b/core/modules/big_pipe/src/Render/BigPipe.php
@@ -155,7 +155,7 @@ protected function sendPreBody($pre_body, array $no_js_placeholders, AttachedAss
 
       $html_response = new HtmlResponse();
       $html_response->setContent([
-        '#markup' => Markup::create($js_bottom_placeholder),
+        '#markup' => BigPipeMarkup::create($js_bottom_placeholder),
         '#attached' => [
           'drupalSettings' => $cumulative_assets->getSettings(),
           'library' => $cumulative_assets->getAlreadyLoadedLibraries(),
@@ -235,7 +235,7 @@ protected function sendNoJsPlaceholders($html, $no_js_placeholders, AttachedAsse
       // @see template_preprocess_html()
       $css_placeholder = '<nojs-bigpipe-placeholder-styles-placeholder token="' . $token . '">';
       $js_placeholder = '<nojs-bigpipe-placeholder-scripts-placeholder token="' . $token . '">';
-      $elements['#markup'] = Markup::create($css_placeholder . $js_placeholder . (string) $elements['#markup']);
+      $elements['#markup'] = BigPipeMarkup::create($css_placeholder . $js_placeholder . (string) $elements['#markup']);
       $elements['#attached']['html_response_attachment_placeholders']['styles'] = $css_placeholder;
       $elements['#attached']['html_response_attachment_placeholders']['scripts'] = $js_placeholder;
 
diff --git a/core/modules/big_pipe/src/Render/BigPipeMarkup.php b/core/modules/big_pipe/src/Render/BigPipeMarkup.php
new file mode 100644
index 0000000..2b96e4a
--- /dev/null
+++ b/core/modules/big_pipe/src/Render/BigPipeMarkup.php
@@ -0,0 +1,28 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\big_pipe\Render\BigPipeMarkup.
+ */
+
+namespace Drupal\big_pipe\Render;
+
+use Drupal\Component\Render\MarkupInterface;
+use Drupal\Component\Render\MarkupTrait;
+
+/**
+ * Defines an object that passes safe strings through the Views render system.
+ *
+ * This object should only be constructed with a known safe string. If there is
+ * any risk that the string contains user-entered data that has not been
+ * filtered first, it must not be used.
+ *
+ * @internal
+ *   This object is marked as internal because it should only be used in the
+ *   BigPipe render pipeline.
+ *
+ * @see \Drupal\Core\Render\Markup
+ */
+final class BigPipeMarkup implements MarkupInterface, \Countable {
+  use MarkupTrait;
+}
diff --git a/core/modules/big_pipe/src/Tests/BigPipePlaceholderTestCases.php b/core/modules/big_pipe/src/Tests/BigPipePlaceholderTestCases.php
index 524e155..8f2f072 100644
--- a/core/modules/big_pipe/src/Tests/BigPipePlaceholderTestCases.php
+++ b/core/modules/big_pipe/src/Tests/BigPipePlaceholderTestCases.php
@@ -7,7 +7,7 @@
 
 namespace Drupal\big_pipe\Tests;
 
-use Drupal\Core\Render\Markup;
+use Drupal\big_pipe\Render\BigPipeMarkup;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\Url;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -173,7 +173,7 @@ public static function cases(ContainerInterface $container = NULL, AccountInterf
     // happens to not be valid HTML.
     $hello = new BigPipePlaceholderTestCase(
       [
-        '#markup' => Markup::create('<hello'),
+        '#markup' => BigPipeMarkup::create('<hello'),
         '#attached' => [
           'placeholders' => [
             '<hello' => ['#lazy_builder' => ['\Drupal\big_pipe_test\BigPipeTestController::helloOrYarhar', []]],
@@ -204,7 +204,7 @@ public static function cases(ContainerInterface $container = NULL, AccountInterf
     // 5. Edge case: non-#lazy_builder placeholder.
     $current_time = new BigPipePlaceholderTestCase(
       [
-        '#markup' => Markup::create('<time>CURRENT TIME</time>'),
+        '#markup' => BigPipeMarkup::create('<time>CURRENT TIME</time>'),
         '#attached' => [
           'placeholders' => [
             '<time>CURRENT TIME</time>' => [
diff --git a/core/modules/big_pipe/tests/modules/big_pipe_test/src/BigPipeTestController.php b/core/modules/big_pipe/tests/modules/big_pipe_test/src/BigPipeTestController.php
index e605a1a..3a663fc 100644
--- a/core/modules/big_pipe/tests/modules/big_pipe_test/src/BigPipeTestController.php
+++ b/core/modules/big_pipe/tests/modules/big_pipe_test/src/BigPipeTestController.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\big_pipe_test;
 
-use Drupal\Core\Render\Markup;
+use Drupal\big_pipe\Render\BigPipeMarkup;
 
 class BigPipeTestController {
 
@@ -58,7 +58,7 @@ public static function currentTime() {
    */
   public static function helloOrYarhar() {
     return [
-      '#markup' => Markup::create('<marquee>Yarhar llamas forever!</marquee>'),
+      '#markup' => BigPipeMarkup::create('<marquee>Yarhar llamas forever!</marquee>'),
       '#cache' => ['max-age' => 0],
     ];
   }