reform: On form error, simple_form association helpers are not filled

I use the following initializer to make association work (as proposed here: https://github.com/apotonick/reform/issues/122):

# /config/initializers/reform.rb
Reform::Form::ModelReflections.module_eval do
    # TODO: This is a hack for making simple_form association inputs work with reform.
    # This should be removed once the problem is fixed in the gems.
    def self.included(base)
        def base.reflect_on_association(*args)
            model_name.to_s.constantize.reflect_on_association(*args)
        end

        super
    end
end

# Form.rb
class Form < Reform::Form
    include ModelReflections
end

And this code for my association:

# ClientForm.rb
class ClientForm < Form
    model :client

    properties :name, :language_ids
end

# _form.html.erb
<%= f.association :languages, as: :check_boxes, collection: Language.all, disabled: [default_language.id] %>

But on error, the content just disappear. If there’s no error, it saves normally and everything is fine!

I use Rails 4.2.3, Simple Form 3.1.0 and Reform 2.0.1. Does someone have an idea what is happening?