diff -u b/core/modules/language/language.module b/core/modules/language/language.module
--- b/core/modules/language/language.module
+++ b/core/modules/language/language.module
@@ -431,7 +431,7 @@
   $language_entity->direction = isset($language->direction) ? $language->direction : '0';
   $language_entity->locked = !empty($language->locked);
   $language_entity->weight = isset($language->weight) ? $language->weight : 0;
-  $language_entity->setDefault(!empty($language->isDefault()));
+  $language_entity->setDefault($language->isDefault());
   $language_entity->save();
   $t_args = array('%language' => $language->name, '%langcode' => $language->getId());
   if ($language_entity->isNew()) {