diff -u b/core/modules/language/lib/Drupal/language/Entity/Language.php b/core/modules/language/lib/Drupal/language/Entity/Language.php
--- b/core/modules/language/lib/Drupal/language/Entity/Language.php
+++ b/core/modules/language/lib/Drupal/language/Entity/Language.php
@@ -125,12 +125,7 @@
    */
   public function isDefault() {
     if (!isset($this->default)) {
-      if (static::getDefaultLangcode() == $this->id()) {
-        return TRUE;
-      }
-      else {
-        return FALSE;
-      }
+      return static::getDefaultLangcode() == $this->id();
     }
     return $this->default;
   }
@@ -156,6 +151,8 @@
   public function postSave(EntityStorageInterface $storage, $update = TRUE) {
     parent::postSave($storage, $update);
 
+    // Only set the default language and save it to system.site configuration if
+    // it needs to updated.
     if ($this->isDefault() && static::getDefaultLangcode() != $this->id()) {
       // Update the config. Saving the configuration fires and event that causes
       // the container to be rebuilt.
@@ -174,8 +171,8 @@
     // flushed.
     language_negotiation_url_prefixes_update();
 
-    // If after adding this language the site will become multilingual, we need to
-    // rebuild language services.
+    // If after adding this language the site will become multilingual, we need
+    // to rebuild language services.
     if (!$this->preSaveMultilingual && !$update && $language_manager instanceof ConfigurableLanguageManagerInterface) {
       $language_manager::rebuildServices();
     }
@@ -207,9 +204,9 @@
    * @throws \RuntimeException
    */
   public static function preDelete(EntityStorageInterface $storage, array $entities) {
-    $default_language = static::getDefaultLangcode();
+    $default_langcode = static::getDefaultLangcode();
     foreach ($entities as $entity) {
-      if ($entity->id() == $default_language->id && !$entity->isUninstalling()) {
+      if ($entity->id() == $default_langcode && !$entity->isUninstalling()) {
         throw new DeleteDefaultLanguageException('Can not delete the default language');
       }
     }