form_rest not show hidden fields

# Twig
<form action="XXX" method="post" {{ form_enctype(form) }}>
    {{ form_widget(form) }}
        <button class="btn" type="submit">{% trans %}private{% endtrans %}</button>
    {{ form_rest(form) }}
</form>

# FomType
XXX
public function buildForm(FormBuilderInterface $builder, array $options)
    {
        parent::buildForm($builder, $options);
        $builder
            ->add('pub', 'hidden')
            ->getForm();
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'MyClass',
            'csrf_protection' => true,
            'csrf_field_name' => '_token',
        ));
    }