'default' => [
                                'admin' => 'ROLE_ADMIN',
                                'civility' => 'Mister',
+                               'languages' => [
+                                       'en_gb' => 'English'
+                               ],
+                               'locales' => [ 'en_gb' ],
                                'group' => [ 'User' ]
                        ],
                        'route' => [
                                ->children()
                                        ->arrayNode('class')
                                                ->addDefaultsIfNotSet()
-                                               ->ignoreExtraKeys()
+                                               #XXX: ignoreExtraKeys(bool $remove = true)
+                                               ->ignoreExtraKeys(false)
                                                ->children()
                                                        ->scalarNode('civility')->cannotBeEmpty()->defaultValue($defaults['class']['civility'])->end()
                                                        ->scalarNode('group')->cannotBeEmpty()->defaultValue($defaults['class']['group'])->end()
                                        ->end()
                                        ->arrayNode('default')
                                                ->addDefaultsIfNotSet()
-                                               ->ignoreExtraKeys()
+                                               #XXX: ignoreExtraKeys(bool $remove = true)
+                                               ->ignoreExtraKeys(false)
                                                ->children()
                                                        ->scalarNode('admin')->cannotBeEmpty()->defaultValue($defaults['default']['admin'])->end()
                                                        ->scalarNode('civility')->cannotBeEmpty()->defaultValue($defaults['default']['civility'])->end()
+                                                       #TODO: see if we can't prevent key normalisation with ->normalizeKeys(false)
+                                                       ->arrayNode('languages')
+                                                               ->treatNullLike([])
+                                                               ->defaultValue($defaults['default']['languages'])
+                                                               ->scalarPrototype()->end()
+                                                       ->end()
+                                                       #TODO: see if we can't prevent key normalisation with ->normalizeKeys(false)
+                                                       ->arrayNode('locales')
+                                                               ->treatNullLike([])
+                                                               ->defaultValue($defaults['default']['locales'])
+                                                               ->scalarPrototype()->end()
+                                                       ->end()
                                                        ->arrayNode('group')
                                                                ->treatNullLike([])
                                                                ->defaultValue($defaults['default']['group'])