diff --git a/core/modules/language/language.services.yml b/core/modules/language/language.services.yml
index 9f1a38f..fa4f4f3 100644
--- a/core/modules/language/language.services.yml
+++ b/core/modules/language/language.services.yml
@@ -13,7 +13,6 @@ services:
       - { name: event_subscriber }
   language.config_factory_override:
     class: Drupal\language\Config\LanguageConfigFactoryOverride
-    arguments: ['@language.default', '@config.storage', '@event_dispatcher', '@config.typed']
+    arguments: ['@config.storage', '@event_dispatcher', '@config.typed']
     tags:
       - { name: config.factory.override, priority: -254 }
-      - { name: persist }
diff --git a/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php
index 113d492..bfadec0 100644
--- a/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php
+++ b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php
@@ -50,10 +50,6 @@ class LanguageConfigFactoryOverride implements LanguageConfigFactoryOverrideInte
   /**
    * Constructs the LanguageConfigFactoryOverride object.
    *
-   * @param \Drupal\Core\Language\LanguageDefault $language_default
-   *   The default language service. This sets the initial language on the
-   *   config factory to the site's default. The language can be used to
-   *   override configuration data if language overrides are available.
    * @param \Drupal\Core\Config\StorageInterface $storage
    *   The configuration storage engine.
    * @param \Symfony\Component\EventDispatcher\EventDispatcherInterface $event_dispatcher
@@ -61,11 +57,7 @@ class LanguageConfigFactoryOverride implements LanguageConfigFactoryOverrideInte
    * @param \Drupal\Core\Config\TypedConfigManagerInterface $typed_config
    *   The typed configuration manager.
    */
-  public function __construct(LanguageDefault $language_default, StorageInterface $storage, EventDispatcherInterface $event_dispatcher, TypedConfigManagerInterface $typed_config) {
-    // Ensure that configuration can be localised if the site is monolingual
-    // but the Language module is enabled. This is the case for monolingual
-    // sites not in English.
-    $this->language = $language_default->get();
+  public function __construct(StorageInterface $storage, EventDispatcherInterface $event_dispatcher, TypedConfigManagerInterface $typed_config) {
     $this->storage = $storage;
     $this->eventDispatcher = $event_dispatcher;
     $this->typedConfigManager = $typed_config;
@@ -147,7 +139,7 @@ protected function getLanguageConfigName($langcode, $name) {
    * {@inheritdoc}
    */
   public function getCacheSuffix() {
-    return $this->language->id;
+    return $this->language ? $this->language->id : NULL;
   }
 
   /**
@@ -165,4 +157,12 @@ public function setLanguage(Language $language = NULL) {
     return $this;
   }
 
+  /**
+   * {@inheritdoc}
+   */
+  public function setLanguageFromDefault(LanguageDefault $language_default = NULL) {
+    $this->language = $language_default ? $language_default->get() : NULL;
+    return $this;
+  }
+
 }
diff --git a/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverrideInterface.php b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverrideInterface.php
index aceff6b..1c3de55 100644
--- a/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverrideInterface.php
+++ b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverrideInterface.php
@@ -9,6 +9,7 @@
 
 use Drupal\Core\Config\ConfigFactoryOverrideInterface;
 use Drupal\Core\Language\Language;
+use Drupal\Core\Language\LanguageDefault;
 
 /**
  * Defines the interface for a configuration factory language override object.
@@ -39,6 +40,16 @@ public function getLanguage();
   public function setLanguage(Language $language = NULL);
 
   /**
+   * Sets the language to be used in configuration overrides from the default.
+   *
+   * @param \Drupal\Core\Language\LanguageDefault $language_default
+   *   The default language.
+   *
+   * @return $this
+   */
+  public function setLanguageFromDefault(LanguageDefault $language_default = NULL);
+
+  /**
    * Get language override for given language and configuration name.
    *
    * @param string $langcode
diff --git a/core/modules/language/lib/Drupal/language/LanguageServiceProvider.php b/core/modules/language/lib/Drupal/language/LanguageServiceProvider.php
index c62b2f0..95eb700 100644
--- a/core/modules/language/lib/Drupal/language/LanguageServiceProvider.php
+++ b/core/modules/language/lib/Drupal/language/LanguageServiceProvider.php
@@ -56,6 +56,14 @@ public function alter(ContainerBuilder $container) {
     if ($default_language_values = $this->getDefaultLanguageValues()) {
       $container->setParameter('language.default_values', $default_language_values);
     }
+
+    // For monolingual sites, we explicitly set the default language for the
+    // language config override service as there is no language negotiation.
+    if (!$this->isMultilingual()) {
+      $container->getDefinition('language.config_factory_override')
+        ->addMethodCall('setLanguageFromDefault', array(new Reference('language.default')));
+    }
+
   }
 
   /**
diff --git a/index.php b/index.php
index 2181fb3..34346bc 100644
--- a/index.php
+++ b/index.php
@@ -8,6 +8,11 @@
  * See COPYRIGHT.txt and LICENSE.txt files in the "core" directory.
  */
 
+$xhprof_path = '/var/www/';
+include_once $xhprof_path . '/xhprof_lib/utils/xhprof_lib.php';
+include_once $xhprof_path . '/xhprof_lib/utils/xhprof_runs.php';
+xhprof_enable(XHPROF_FLAGS_NO_BUILTINS + XHPROF_FLAGS_MEMORY);
+
 require_once __DIR__ . '/core/vendor/autoload.php';
 require_once __DIR__ . '/core/includes/bootstrap.inc';
 
@@ -23,3 +28,9 @@
   print $message;
   throw $e;
 }
+
+$xhprof_data = xhprof_disable();
+$xhprof_runs = new XHProfRuns_Default();
+$namespace = 'd8';
+$id = $xhprof_runs->save_run($xhprof_data, $namespace);
+print "<a href='http://localhost/xhprof_html/?run=$id&sort=excl_wt&source=$namespace'>XHPROF</a>";