diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 616637c..36b3c05 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -21,7 +21,7 @@
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
 
-use Guzzle\Http\Exception\RequestException;
+use GuzzleHttp\Exception\RequestException;
 
 /**
  * @file
@@ -1580,8 +1580,8 @@ function install_retrieve_file($uri, $destination) {
   }
 
   try {
-    $request = \Drupal::httpClient()->get($uri, array('Accept' => 'text/plain'));
-    $data = $request->send()->getBody(TRUE);
+    $request = \Drupal::httpClient()->get($uri, array('headers' => array('Accept' => 'text/plain')));
+    $data = $request->getBody(TRUE);
     if (empty($data)) {
       return FALSE;
     }
diff --git a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/fetcher/DefaultFetcher.php b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/fetcher/DefaultFetcher.php
index 611fc46..d839df1 100644
--- a/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/fetcher/DefaultFetcher.php
+++ b/core/modules/aggregator/lib/Drupal/aggregator/Plugin/aggregator/fetcher/DefaultFetcher.php
@@ -69,7 +69,7 @@ public function fetch(FeedInterface $feed) {
     }
 
     try {
-      $response = $request->send();
+      $response = $this->httpClient->send($request);
 
       // In case of a 304 Not Modified, there is no new content, so return
       // FALSE.
diff --git a/core/modules/aggregator/tests/modules/aggregator_test/lib/Drupal/aggregator_test/Plugin/aggregator/fetcher/TestFetcher.php b/core/modules/aggregator/tests/modules/aggregator_test/lib/Drupal/aggregator_test/Plugin/aggregator/fetcher/TestFetcher.php
index 8aaf8e0..8c06a96 100644
--- a/core/modules/aggregator/tests/modules/aggregator_test/lib/Drupal/aggregator_test/Plugin/aggregator/fetcher/TestFetcher.php
+++ b/core/modules/aggregator/tests/modules/aggregator_test/lib/Drupal/aggregator_test/Plugin/aggregator/fetcher/TestFetcher.php
@@ -10,7 +10,6 @@
 use Drupal\aggregator\Plugin\FetcherInterface;
 use Drupal\aggregator\Plugin\aggregator\fetcher\DefaultFetcher;
 use Drupal\aggregator\FeedInterface;
-use Guzzle\Http\Exception\BadResponseException;
 
 /**
  * Defines a test fetcher implementation.
diff --git a/core/modules/locale/locale.batch.inc b/core/modules/locale/locale.batch.inc
index 5085a2b..ae0ea48 100644
--- a/core/modules/locale/locale.batch.inc
+++ b/core/modules/locale/locale.batch.inc
@@ -5,8 +5,7 @@
  *   Batch process to check the availability of remote or local po files.
  */
 
-use Guzzle\Http\Exception\BadResponseException;
-use Guzzle\Http\Exception\RequestException;
+use GuzzleHttp\Exception\RequestException;
 
 /**
  * Load the common translation API.
@@ -231,9 +230,7 @@ function locale_translation_batch_fetch_finished($success, $results) {
 function locale_translation_http_check($uri) {
 
   try {
-    $response = \Drupal::httpClient()
-      ->head($uri)
-      ->send();
+    $response = \Drupal::httpClient()->head($uri);
     $result = array();
 
     // Return the effective URL if it differs from the requested.
@@ -244,7 +241,7 @@ function locale_translation_http_check($uri) {
     $result['last_modified'] = $response->getLastModified() ? strtotime($response->getLastModified()) : 0;
     return $result;
   }
-  catch (BadResponseException $e) {
+  catch (RequestException $e) {
     // Handle 4xx and 5xx http responses.
     $response = $e->getResponse();
     if ($response->getStatusCode() == 404) {
@@ -258,11 +255,7 @@ function locale_translation_http_check($uri) {
     }
     watchdog('locale', 'HTTP request to @url failed with error: @error.', array('@url' => $uri, '@error' => $response->getStatusCode() . ' ' . $response->getReasonPhrase()));
   }
-  catch (RequestException $e) {
-    // Handle connection problems and cURL specific errors (CurlException) and
-    // other http related errors.
-    watchdog('locale', 'HTTP request to @url failed with error: @error.', array('@url' => $uri, '@error' => $e->getMessage()));
-  }
+
   return FALSE;
 }
 
diff --git a/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsReportsTest.php b/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsReportsTest.php
index e1dc9f6..9f90a27 100644
--- a/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsReportsTest.php
+++ b/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsReportsTest.php
@@ -37,7 +37,7 @@ function testPopularContentBlock() {
     global $base_url;
     $stats_path = $base_url . '/' . drupal_get_path('module', 'statistics'). '/statistics.php';
     $client = \Drupal::httpClient();
-    $client->setConfig(array('curl.options' => array(CURLOPT_TIMEOUT => 10)));
+    $client->setDefaultOption('config/curl', array(CURLOPT_TIMEOUT => 10));
     $client->post($stats_path, $headers, $post)->send();
 
     // Configure and save the block.
diff --git a/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsTokenReplaceTest.php b/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsTokenReplaceTest.php
index 712c5ab..e6d17cb 100644
--- a/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsTokenReplaceTest.php
+++ b/core/modules/statistics/lib/Drupal/statistics/Tests/StatisticsTokenReplaceTest.php
@@ -41,7 +41,7 @@ function testStatisticsTokenReplacement() {
     global $base_url;
     $stats_path = $base_url . '/' . drupal_get_path('module', 'statistics'). '/statistics.php';
     $client = \Drupal::httpClient();
-    $client->setConfig(array('curl.options' => array(CURLOPT_TIMEOUT => 10)));
+    $client->setDefaultOption('config/curl', array(CURLOPT_TIMEOUT => 10));
     $client->post($stats_path, $headers, $post)->send();
     $statistics = statistics_get($node->id());
 
diff --git a/core/modules/statistics/lib/Drupal/statistics/Tests/Views/IntegrationTest.php b/core/modules/statistics/lib/Drupal/statistics/Tests/Views/IntegrationTest.php
index 7d3e567..e417f27 100644
--- a/core/modules/statistics/lib/Drupal/statistics/Tests/Views/IntegrationTest.php
+++ b/core/modules/statistics/lib/Drupal/statistics/Tests/Views/IntegrationTest.php
@@ -83,8 +83,8 @@ public function testNodeCounterIntegration() {
     global $base_url;
     $stats_path = $base_url . '/' . drupal_get_path('module', 'statistics'). '/statistics.php';
     $client = \Drupal::httpClient();
-    $client->setConfig(array('curl.options' => array(CURLOPT_TIMEOUT => 10)));
-    $client->post($stats_path, array(), array('nid' => $this->node->id()))->send();
+    $client->setDefaultOption('config/curl', array(CURLOPT_TIMEOUT => 10));
+    $client->post($stats_path, array(), array('nid' => $this->node->id()));
     $this->drupalGet('test_statistics_integration');
 
     $expected = statistics_get($this->node->id());
diff --git a/core/modules/system/system.module b/core/modules/system/system.module
index 7b35fca..b08039e 100644
--- a/core/modules/system/system.module
+++ b/core/modules/system/system.module
@@ -18,8 +18,7 @@
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Response;
 use Symfony\Component\HttpFoundation\Request;
-use Guzzle\Http\Exception\BadResponseException;
-use Guzzle\Http\Exception\RequestException;
+use GuzzleHttp\Exception\RequestException;
 
 /**
  * Maximum age of temporary files in seconds.
@@ -1690,11 +1689,6 @@ function system_retrieve_file($url, $destination = NULL, $managed = FALSE, $repl
       ->getBody(TRUE);
     $local = $managed ? file_save_data($data, $path, $replace) : file_unmanaged_save_data($data, $path, $replace);
   }
-  catch (BadResponseException $exception) {
-    $response = $exception->getResponse();
-    drupal_set_message(t('Failed to fetch file due to HTTP error "%error"', array('%error' => $response->getStatusCode() . ' ' . $response->getReasonPhrase())), 'error');
-    return FALSE;
-  }
   catch (RequestException $exception) {
     drupal_set_message(t('Failed to fetch file due to error "%error"', array('%error' => $exception->getMessage())), 'error');
     return FALSE;
diff --git a/core/modules/update/tests/Drupal/update/Tests/UpdateFetcherTest.php b/core/modules/update/tests/Drupal/update/Tests/UpdateFetcherTest.php
index e43a3ae..4b55261 100644
--- a/core/modules/update/tests/Drupal/update/Tests/UpdateFetcherTest.php
+++ b/core/modules/update/tests/Drupal/update/Tests/UpdateFetcherTest.php
@@ -39,7 +39,7 @@ public static function getInfo() {
    */
   protected function setUp() {
     $config_factory = $this->getConfigFactoryStub(array('update.settings' => array('fetch_url' => 'http://www.example.com')));
-    $this->updateFetcher = new UpdateFetcher($config_factory, $this->getMock('Guzzle\Http\Client'));
+    $this->updateFetcher = new UpdateFetcher($config_factory, $this->getMock('Drupal\Core\Http\Client'));
   }
 
   /**
diff --git a/core/modules/xmlrpc/xmlrpc.inc b/core/modules/xmlrpc/xmlrpc.inc
index 445993a..cb2180e 100644
--- a/core/modules/xmlrpc/xmlrpc.inc
+++ b/core/modules/xmlrpc/xmlrpc.inc
@@ -11,8 +11,7 @@
  * This version is made available under the GNU GPL License
  */
 
-use Guzzle\Http\Exception\BadResponseException;
-use Guzzle\Http\Exception\RequestException;
+use GuzzleHttp\Exception\RequestException;
 
 /**
  * Turns a data structure into objects with 'data' and 'type' attributes.
@@ -561,15 +560,11 @@ function _xmlrpc($url, array $args, array $headers = array()) {
     $args = $args[$method];
   }
   $xmlrpc_request = xmlrpc_request($method, $args);
-  $request = \Drupal::httpClient()->post($url, $headers, $xmlrpc_request->xml);
-  $request->setHeader('Content-Type', 'text/xml');
+
+  $headers['Content-Type'] = 'text/xml';
+
   try {
-    $response = $request->send();
-  }
-  catch (BadResponseException $exception) {
-    $response = $exception->getResponse();
-    xmlrpc_error($response->getStatusCode(), $response->getReasonPhrase());
-    return FALSE;
+    $response = \Drupal::httpClient()->post($url, array('headers' => $headers, 'body' => $xmlrpc_request->xml));
   }
   catch (RequestException $exception) {
     xmlrpc_error(NULL, $exception->getMethod());