diff --git a/core/core.services.yml b/core/core.services.yml
index ef9ccd8..29ac197 100644
--- a/core/core.services.yml
+++ b/core/core.services.yml
@@ -380,7 +380,7 @@ services:
     factory: [GuzzleHttp\HandlerStack, create]
   http_client:
     class: Drupal\Core\Http\Client
-    arguments: ['@http_handler_stack']
+    arguments: ['@http_handler_stack', '@service_container']
   theme.negotiator:
     class: Drupal\Core\Theme\ThemeNegotiator
     arguments: ['@access_check.theme']
diff --git a/core/lib/Drupal/Core/DependencyInjection/Compiler/GuzzleHandlerPass.php b/core/lib/Drupal/Core/DependencyInjection/Compiler/GuzzleHandlerPass.php
index d6dedbf..009e8b2 100644
--- a/core/lib/Drupal/Core/DependencyInjection/Compiler/GuzzleHandlerPass.php
+++ b/core/lib/Drupal/Core/DependencyInjection/Compiler/GuzzleHandlerPass.php
@@ -17,10 +17,9 @@ class GuzzleHandlerPass implements CompilerPassInterface {
    * {@inheritdoc}
    */
   public function process(ContainerBuilder $container) {
-    foreach ($container->findTaggedServiceIds('http_client_handler') as $id => $attributes) {
-      $container->getDefinition('http_handler_stack')
-        ->addMethodCall('push', [new Reference($id)]);
-    }
+    $service_ids = array_keys($container->findTaggedServiceIds('http_client_handler'));
+    $container->getDefinition('http_client')
+      ->addArgument($service_ids);
   }
 
 }
diff --git a/core/lib/Drupal/Core/Http/Client.php b/core/lib/Drupal/Core/Http/Client.php
index afcd8ce..c6b8da6 100644
--- a/core/lib/Drupal/Core/Http/Client.php
+++ b/core/lib/Drupal/Core/Http/Client.php
@@ -15,6 +15,7 @@
 use GuzzleHttp\Middleware;
 use Psr\Http\Message\RequestInterface;
 use Psr\Http\Message\ResponseInterface;
+use Symfony\Component\DependencyInjection\ContainerInterface;
 
 /**
  * Drupal default HTTP client class.
@@ -26,7 +27,10 @@ class Client extends GuzzleClient {
   /**
    * {@inheritdoc}
    */
-  public function __construct(HandlerStack $stack, array $config = []) {
+  public function __construct(HandlerStack $stack, ContainerInterface $container, array $service_ids = []) {
+    foreach ($service_ids as $id) {
+      $stack->push($container->get($id)->register());
+    }
     $stack->after('allow_redirects', Middleware::mapRequest(function (RequestInterface $request) {
       $this->effectiveUrl = $request->getUri();
       return $request;
@@ -52,7 +56,7 @@ public function __construct(HandlerStack $stack, array $config = []) {
     // The entire config array is merged/configurable to allow Guzzle client
     // options outside of 'defaults' to be changed, such as 'adapter', or
     // 'message_factory'.
-    $config = NestedArray::mergeDeep(array('defaults' => $default_config), $config, Settings::get('http_client_config', array()));
+    $config = NestedArray::mergeDeep(array('defaults' => $default_config), Settings::get('http_client_config', array()));
 
     parent::__construct($config['defaults']);
   }
diff --git a/core/lib/Drupal/Core/Http/StackHandlerRegistrationInterface.php b/core/lib/Drupal/Core/Http/StackHandlerRegistrationInterface.php
new file mode 100644
index 0000000..948bf02
--- /dev/null
+++ b/core/lib/Drupal/Core/Http/StackHandlerRegistrationInterface.php
@@ -0,0 +1,20 @@
+<?php
+/**
+ * @file
+ * Contains StackHandlerRegistrationInterface.php
+ */
+
+namespace Drupal\Core\Http;
+
+
+interface StackHandlerRegistrationInterface {
+
+  /**
+   * Registers a new callable in the http_client stack handler.
+   *
+   * @return callable
+   *   Returns a callable to be pushed onto the HandlerStack.
+   */
+  public function register();
+
+}
diff --git a/core/lib/Drupal/Core/Test/EventSubscriber/HttpRequestSubscriber.php b/core/lib/Drupal/Core/Test/EventSubscriber/HttpRequestSubscriber.php
index 2cb8299..b001638 100644
--- a/core/lib/Drupal/Core/Test/EventSubscriber/HttpRequestSubscriber.php
+++ b/core/lib/Drupal/Core/Test/EventSubscriber/HttpRequestSubscriber.php
@@ -7,24 +7,26 @@
 
 namespace Drupal\Core\Test\EventSubscriber;
 
+use Drupal\Core\Http\StackHandlerRegistrationInterface;
+use GuzzleHttp\HandlerStack;
 use Psr\Http\Message\RequestInterface;
 
 /**
  * Overrides the User-Agent HTTP header for outbound HTTP requests.
  */
-class HttpRequestSubscriber {
+class HttpRequestSubscriber implements StackHandlerRegistrationInterface {
 
   /**
    * {@inheritdoc}
    */
-  public function __invoke($name) {
+  public function register() {
     // If the database prefix is being used by SimpleTest to run the tests in a copied
     // database then set the user-agent header to the database prefix so that any
     // calls to other Drupal pages will run the SimpleTest prefixed database. The
     // user-agent is used to ensure that multiple testing sessions running at the
     // same time won't interfere with each other as they would if the database
     // prefix were stored statically in a file or database variable.
-    return function (callable $handler) {
+    return function ($handler) {
       return function (RequestInterface $request, array $options) use ($handler) {
         if ($test_prefix = drupal_valid_test_ua()) {
           $request = $request->withHeader('User-Agent', drupal_generate_test_ua($test_prefix));
diff --git a/core/modules/aggregator/src/Plugin/aggregator/fetcher/DefaultFetcher.php b/core/modules/aggregator/src/Plugin/aggregator/fetcher/DefaultFetcher.php
index 2434b74..80d36bd 100644
--- a/core/modules/aggregator/src/Plugin/aggregator/fetcher/DefaultFetcher.php
+++ b/core/modules/aggregator/src/Plugin/aggregator/fetcher/DefaultFetcher.php
@@ -92,8 +92,12 @@ public function fetch(FeedInterface $feed) {
       }
 
       $feed->source_string = (string) $response->getBody();
-      $feed->setEtag($response->getHeader('ETag')[0]);
-      $feed->setLastModified(strtotime($response->getHeader('Last-Modified')[0]));
+      if ($response->hasHeader('ETag')) {
+        $feed->setEtag($response->getHeader('ETag')[0]);
+      }
+      if ($response->hasHeader('Last-Modified')) {
+        $feed->setLastModified(strtotime($response->getHeader('Last-Modified')[0]));
+      }
       $feed->http_headers = $response->getHeaders();
 
       // Update the feed URL in case of a 301 redirect.
diff --git a/core/modules/locale/locale.batch.inc b/core/modules/locale/locale.batch.inc
index 95333eb..7c1c122 100644
--- a/core/modules/locale/locale.batch.inc
+++ b/core/modules/locale/locale.batch.inc
@@ -238,9 +238,9 @@ function locale_translation_http_check($uri) {
     $result = array();
 
     // Return the effective URL if it differs from the requested.
-//    if ($response->getEffectiveUrl() != $uri) {
-//      $result['location'] = $response->getEffectiveUrl();
-//    }
+    if ($response->hasHeader('X-Effective-Url') && $response->getHeader('X-Effective-Url')[0] != $uri) {
+      $result['location'] = $response->getHeader('X-Effective-Url')[0];
+    }
 
     $result['last_modified'] = $response->hasHeader('Last-Modified') ? strtotime($response->getHeader('Last-Modified')[0]) : 0;
     return $result;