JRuby::Rack with Rails send_file bug

rackup.ru

require 'rubygems'
%w(action_controller/railtie).map &method(:require)

class JrubyRackTest < Rails::Application
  config.secret_token = routes.append { root :to => 'send_file#deliver' }.inspect
  initialize!
end

run JrubyRackTest

class SendFileController < ActionController::Base
  def deliver
    if params[:txt]
      send_file Rails.root.join("synaptic.txt")
    else
      send_file Rails.root.join("image.jpg")
    end
  end
end