diff --git a/core/lib/Drupal/Core/DrupalKernel.php b/core/lib/Drupal/Core/DrupalKernel.php
index 5ea2040..0c80fae 100644
--- a/core/lib/Drupal/Core/DrupalKernel.php
+++ b/core/lib/Drupal/Core/DrupalKernel.php
@@ -211,7 +211,7 @@ class DrupalKernel implements DrupalKernelInterface, TerminableInterface {
   public static function createFromRequest(Request $request, $class_loader, $environment, $allow_dumping = TRUE) {
     $kernel = new static($environment, $class_loader, $allow_dumping);
     static::bootEnvironment();
-    $this->initializeSettings($request);
+    $kernel->initializeSettings($request);
     return $kernel;
   }
 
@@ -599,6 +599,9 @@ public function handle(Request $request, $type = self::MASTER_REQUEST, $catch =
       $response = new Response($message, 500);
     }
 
+    // Adapt response headers to the current request.
+    $response->prepare($request);
+
     return $response;
   }
 
diff --git a/core/lib/Drupal/Core/Test/TestRunnerKernel.php b/core/lib/Drupal/Core/Test/TestRunnerKernel.php
index 0b2f790..684a83b 100644
--- a/core/lib/Drupal/Core/Test/TestRunnerKernel.php
+++ b/core/lib/Drupal/Core/Test/TestRunnerKernel.php
@@ -37,6 +37,8 @@ public function __construct($environment, $class_loader) {
     //   \Drupal\Core\Datetime\DateFormatter has a (needless) dependency on the
     //   'date_format' entity, so calls to format_date()/format_interval() cause
     //   a plugin not found exception.
+    $core_root = dirname(dirname(dirname(dirname(__DIR__))));
+    require_once $core_root . '/includes/bootstrap.inc';
     $this->moduleList = array(
       'system' => 0,
       'simpletest' => 0,
diff --git a/core/modules/system/tests/http.php b/core/modules/system/tests/http.php
index dff8a9e..5cdf74a 100644
--- a/core/modules/system/tests/http.php
+++ b/core/modules/system/tests/http.php
@@ -27,7 +27,6 @@
 
 $request = Request::createFromGlobals();
 $response = $kernel->handle($request);
-$response->prepare($request);
 $response->send();
 
 $kernel->terminate($request, $response);
diff --git a/core/modules/system/tests/https.php b/core/modules/system/tests/https.php
index 7d32639..fb5cda8 100644
--- a/core/modules/system/tests/https.php
+++ b/core/modules/system/tests/https.php
@@ -29,7 +29,6 @@
 
 $request = Request::createFromGlobals();
 $response = $kernel->handle($request);
-$response->prepare($request);
 $response->send();
 
 $kernel->terminate($request, $response);
diff --git a/index.php b/index.php
index 90b99b3..8d88b1c 100644
--- a/index.php
+++ b/index.php
@@ -17,7 +17,6 @@
 
 $request = Request::createFromGlobals();
 $response = $kernel->handle($request);
-$response->prepare($request);
 $response->send();
 
 $kernel->terminate($request, $response);