diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 0c7c353..d3cd7b5 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1559,8 +1559,10 @@ function install_download_additional_translations(&$install_state) {
   }
   $language->save();
 
-  // If a non-English language was selected, remove English.
+  // If a non-English language was selected, change the default language and
+  // remove English.
   if ($langcode != 'en') {
+    \Drupal::config('system.site')->set('langcode', $langcode)->save();
     entity_delete_multiple('configurable_language', array('en'));
   }