diff --git a/core/modules/config_translation/lib/Drupal/config_translation/Form/ConfigTranslationFormBase.php b/core/modules/config_translation/lib/Drupal/config_translation/Form/ConfigTranslationFormBase.php
index 4d2bd68..851a9b2 100644
--- a/core/modules/config_translation/lib/Drupal/config_translation/Form/ConfigTranslationFormBase.php
+++ b/core/modules/config_translation/lib/Drupal/config_translation/Form/ConfigTranslationFormBase.php
@@ -16,6 +16,7 @@
 use Drupal\Core\Form\BaseFormIdInterface;
 use Drupal\Core\Form\FormBase;
 use Drupal\Core\Language\Language;
+use Drupal\language\Config\LanguageConfigOverride;
 use Drupal\language\ConfigurableLanguageManagerInterface;
 use Drupal\locale\StringStorageInterface;
 use Symfony\Component\DependencyInjection\ContainerInterface;
@@ -355,7 +356,7 @@ protected function buildConfigForm(Element $schema, $config_data, $base_config_d
    *   Set the configuration in this language.
    * @param \Drupal\Core\Config\Config $base_config
    *   Base configuration values, in the source language.
-   * @param \Drupal\Core\Config\Config $config_translation
+   * @param \Drupal\language\Config\LanguageConfigOverride $config_translation
    *   Translation configuration override data.
    * @param array $config_values
    *   A simple one dimensional or recursive array:
@@ -375,7 +376,7 @@ protected function buildConfigForm(Element $schema, $config_data, $base_config_d
    * @return array
    *   Translation configuration override data.
    */
-  protected function setConfig(Language $language, Config $base_config, Config $config_translation, array $config_values, $shipped_config = FALSE) {
+  protected function setConfig(Language $language, Config $base_config, LanguageConfigOverride $config_translation, array $config_values, $shipped_config = FALSE) {
     foreach ($config_values as $key => $value) {
       if (is_array($value) && !isset($value['translation'])) {
         // Traverse into this level in the configuration.
diff --git a/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php
index 340352f..bc3c034 100644
--- a/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php
+++ b/core/modules/language/lib/Drupal/language/Config/LanguageConfigFactoryOverride.php
@@ -113,7 +113,7 @@ public function getLanguage() {
    */
   public function setLanguage(Language $language = NULL) {
     $this->language = $language;
-    $this->storage->setLangcode($this->language->id);
+    $this->storage->setLangcode($this->language ? $this->language->id : NULL);
     return $this;
   }