->addDefaultsIfNotSet()
                                ->children()
                                        ->arrayNode('class')
-                                               ->addDefaultsIfNotSet()
-                                               ->children()
-                                                       ->scalarNode('group')->cannotBeEmpty()->defaultValue($defaults['class']['group'])->end()
-                                                       ->scalarNode('civility')->cannotBeEmpty()->defaultValue($defaults['class']['civility'])->end()
-                                                       ->scalarNode('user')->cannotBeEmpty()->defaultValue($defaults['class']['user'])->end()
-                                               ->end()
+                                               ->treatNullLike([])
+                                               ->defaultValue($defaults['class'])
+                                               ->scalarPrototype()->end()
                                        ->end()
                                        ->arrayNode('default')
                                                ->addDefaultsIfNotSet()