diff --git a/src/Drupal/DrupalExtension/ServiceContainer/DrupalExtension.php b/src/Drupal/DrupalExtension/ServiceContainer/DrupalExtension.php
index e0d187e3..9924d5fe 100644
--- a/src/Drupal/DrupalExtension/ServiceContainer/DrupalExtension.php
+++ b/src/Drupal/DrupalExtension/ServiceContainer/DrupalExtension.php
@@ -123,6 +123,7 @@ public function configure(ArrayNodeDefinition $builder)
               . '  password_field: "Enter your password"' . PHP_EOL
               . '  username_field: "Nickname"'
           )->
+          ignoreExtraKeys(false)->
           addDefaultsIfNotSet()->
           children()->
             scalarNode('login_url')->
@@ -146,6 +147,7 @@ public function configure(ArrayNodeDefinition $builder)
           end()->
         end()->
         arrayNode('selectors')->
+          ignoreExtraKeys(false)->
           addDefaultsIfNotSet()->
           children()->
             scalarNode('message_selector')->end()->