layout is rendered by default for xhr request

Having in controller this one:

def attach_new
  @task_id = params[:id]
end

and in attach_new.js.rjs:

page.replace_html(:upload_controls, :partial => 'attach_new', :object => @task_id)
page[:upload_dialog].show
page[:shadier].show

I'm getting the response which contains the application layout rendered. Is this right behavior?