diff --git a/core/modules/language/language.module b/core/modules/language/language.module
index f66bff2..32ab44c 100644
--- a/core/modules/language/language.module
+++ b/core/modules/language/language.module
@@ -332,7 +332,10 @@ function language_language_types_info() {
  * Reads language prefixes and uses the langcode if no prefix is set.
  */
 function language_negotiation_url_prefixes() {
-  return \Drupal::config('language.negotiation')->get('url.prefixes');
+  // Should always return data without overrides.
+  return \Drupal::configFactory()
+    ->getEditable('language.negotiation')
+    ->get('url.prefixes');
 }
 
 /**
@@ -368,7 +371,10 @@ function language_negotiation_url_prefixes_save(array $prefixes) {
  * Reads language domains.
  */
 function language_negotiation_url_domains() {
-  return \Drupal::config('language.negotiation')->get('url.domains');
+  // Should always return data without overrides.
+  return \Drupal::configFactory()
+    ->getEditable('language.negotiation')
+    ->get('url.domains');
 }
 
 /**
diff --git a/core/modules/language/src/Form/NegotiationUrlForm.php b/core/modules/language/src/Form/NegotiationUrlForm.php
index 49110a3..7ed6bd7 100644
--- a/core/modules/language/src/Form/NegotiationUrlForm.php
+++ b/core/modules/language/src/Form/NegotiationUrlForm.php
@@ -209,12 +209,11 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
     // Save selected format (prefix or domain).
     $this->config('language.negotiation')
       ->set('url.source', $form_state->getValue('language_negotiation_url_part'))
+      // Save new domain and prefix values.
+      ->set('url.prefixes', $form_state->getValue('prefix'))
+      ->set('url.domains', $form_state->getValue('domain'))
       ->save();
 
-    // Save new domain and prefix values.
-    language_negotiation_url_prefixes_save($form_state->getValue('prefix'));
-    language_negotiation_url_domains_save($form_state->getValue('domain'));
-
     parent::submitForm($form, $form_state);
   }
 
diff --git a/core/modules/system/src/Tests/ParamConverter/UpcastingTest.php b/core/modules/system/src/Tests/ParamConverter/UpcastingTest.php
index 95a7eab..3fa73a2 100644
--- a/core/modules/system/src/Tests/ParamConverter/UpcastingTest.php
+++ b/core/modules/system/src/Tests/ParamConverter/UpcastingTest.php
@@ -67,7 +67,9 @@ public function testSameTypes() {
   public function testEntityLanguage() {
     $language = ConfigurableLanguage::createFromLangcode('de');
     $language->save();
-    language_negotiation_url_prefixes_save(array('de' => 'de'));
+    \Drupal::configFactory()->getEditable('language.negotiation')
+      ->set('url.prefixes', array('de' => 'de'))
+      ->save();
 
     // The container must be recreated after adding a new language.
     $this->rebuildContainer();