I don't think it's possible to do this with an appended root. Why don't you include the locale stuff in here? Otherwise, do something like:

````php
$node
    // ... all the stuff you have here above
;

$this->addLocalesSection($node);

public ufnciton addLocalesSection(ArrayNodeDefinition $node)
{
    $node
        ->fixXmlConfig('locale')
        ->children()
            ->arrayNode('locales')
                ->prototype('array')
                    ->prototype('scalar')->end()
                ->end()
            ->end() // locales
        ->end();
}
````