diff --git a/DependencyInjection/Configuration.php b/DependencyInjection/Configuration.php
index <HASH>..<HASH> 100644
--- a/DependencyInjection/Configuration.php
+++ b/DependencyInjection/Configuration.php
@@ -42,12 +42,14 @@ class Configuration implements ConfigurationInterface
                 ->end()
 
                 ->arrayNode('persistence')
+                    ->addDefaultsIfNotSet()
                     ->children()
                         ->scalarNode('class')
                             ->isRequired()
                             ->defaultValue('Liip\TranslationBundle\Persistence\YamlFilePersistence')
                         ->end()
                         ->arrayNode('options')
+                            ->addDefaultsIfNotSet()
                             ->children()
                                 ->scalarNode('folder')
                                     ->defaultValue("%kernel.root_dir%/data/translations")
The persistence options are required by the LiipTranslationExtension. Fixes an "undefined index" issue when clearing the cache.