diff --git a/core/modules/language/language.module b/core/modules/language/language.module
index 6a17f73..845407d 100644
--- a/core/modules/language/language.module
+++ b/core/modules/language/language.module
@@ -431,9 +431,7 @@ function language_save($language) {
   $language_entity->direction = isset($language->direction) ? $language->direction : '0';
   $language_entity->locked = !empty($language->locked);
   $language_entity->weight = isset($language->weight) ? $language->weight : 0;
-
-  // Save the record and inform others about the change.
-  $multilingual = \Drupal::languageManager()->isMultilingual();
+  $language_entity->setDefault(!empty($language->default));
   $language_entity->save();
   $t_args = array('%language' => $language->name, '%langcode' => $language->id);
   if ($language->is_new) {
@@ -443,30 +441,6 @@ function language_save($language) {
     watchdog('language', 'The %language (%langcode) language has been updated.', $t_args);
   }
 
-  if (!empty($language->default)) {
-    // Update the config. Saving the configuration fires and event that causes
-    // the container to be rebuilt.
-    \Drupal::config('system.site')->set('langcode', $language->id)->save();
-    \Drupal::service('language.default')->set($language);
-  }
-
-  $language_manager = \Drupal::languageManager();
-  $language_manager->reset();
-  if ($language_manager instanceof ConfigurableLanguageManagerInterface) {
-    $language_manager->updateLockedLanguageWeights();
-  }
-
-  // Update URL Prefixes for all languages after the new default language is
-  // propagated and the LanguageManagerInterface::getLanguages() cache is
-  // flushed.
-  language_negotiation_url_prefixes_update();
-
-  // If after adding this language the site will become multilingual, we need to
-  // rebuild language services.
-  if (!$multilingual && $language->is_new) {
-    ConfigurableLanguageManager::rebuildServices();
-  }
-
   return $language;
 }
 
diff --git a/core/modules/language/lib/Drupal/language/Entity/Language.php b/core/modules/language/lib/Drupal/language/Entity/Language.php
index 77015cd..6f3f6ac 100644
--- a/core/modules/language/lib/Drupal/language/Entity/Language.php
+++ b/core/modules/language/lib/Drupal/language/Entity/Language.php
@@ -7,8 +7,11 @@
 
 namespace Drupal\language\Entity;
 
+use Drupal\Core\Language\Language as LanguageObject;
 use Drupal\Core\Config\Entity\ConfigEntityBase;
 use Drupal\Core\Entity\EntityStorageInterface;
+use Drupal\language\ConfigurableLanguageManager;
+use Drupal\language\ConfigurableLanguageManagerInterface;
 use Drupal\language\Exception\DeleteDefaultLanguageException;
 use Drupal\language\LanguageInterface;
 
@@ -78,10 +81,45 @@ class Language extends ConfigEntityBase implements LanguageInterface {
   public $locked = FALSE;
 
   /**
+   * Default site language.
+   *
+   * This property is not saved to the language entity since there can be only
+   * one default language. It is saved to system.site:langcode and set on the
+   * container using the language.default service in
+   * \Drupal\language\Entity\Language::postSave().
+   *
+   * @var bool
+   */
+  protected $default = FALSE;
+
+  /**
+   * Used to detect when the site becomes multilingual.
+   *
+   * This property is not saved to the language entity, but is needed for
+   * detecting when to rebuild the services.
+   *
+   * @var bool
+   */
+  protected $preSaveMultilingual;
+
+  /**
+   * Sets the default flag on the language entity.
+   *
+   * @param bool $default
+   */
+  public function setDefault($default) {
+    $this->default = $default;
+  }
+
+  /**
    * {@inheritdoc}
    */
   public function preSave(EntityStorageInterface $storage) {
     parent::preSave($storage);
+    // Store whether or not the site is already multilingual so that we can
+    // rebuild services if necessary during
+    // \Drupal\language\Entity\Language::postSave().
+    $this->preSaveMultilingual = \Drupal::languageManager()->isMultilingual();
     // Languages are picked from a predefined list which is given in English.
     // For the uncommon case of custom languages the label should be given in
     // English.
@@ -90,6 +128,54 @@ public function preSave(EntityStorageInterface $storage) {
 
   /**
    * {@inheritdoc}
+   */
+  public function postSave(EntityStorageInterface $storage, $update = TRUE) {
+    parent::postSave($storage, $update);
+
+    if (!empty($this->default)) {
+      // Update the config. Saving the configuration fires and event that causes
+      // the container to be rebuilt.
+      \Drupal::config('system.site')->set('langcode', $this->id())->save();
+      \Drupal::service('language.default')->set($this->toLanguageObject());
+    }
+
+    $language_manager = \Drupal::languageManager();
+    $language_manager->reset();
+    if ($language_manager instanceof ConfigurableLanguageManagerInterface) {
+      $language_manager->updateLockedLanguageWeights();
+    }
+
+    // Update URL Prefixes for all languages after the new default language is
+    // propagated and the LanguageManagerInterface::getLanguages() cache is
+    // flushed.
+    language_negotiation_url_prefixes_update();
+
+    // If after adding this language the site will become multilingual, we need to
+    // rebuild language services.
+    if (!$this->preSaveMultilingual && !$update) {
+      ConfigurableLanguageManager::rebuildServices();
+    }
+  }
+
+  /**
+   * Converts the Language entity to a Language value object.
+   *
+   * @return \Drupal\Core\Language\Language
+   *   The language configuration entity expressed as a Language value object.
+   */
+  protected function toLanguageObject() {
+    return new LanguageObject(array(
+      'id' => $this->id(),
+      'name' => $this->label(),
+      'direction' => $this->direction,
+      'weight' => $this->weight,
+      'locked' => $this->locked,
+      'default' => $this->default,
+    ));
+  }
+
+  /**
+   * {@inheritdoc}
    *
    * @throws \RuntimeException
    */