Rack test problem

output.txt

$ ruby rack_proxy.rb 
Loaded suite rack_proxy
Started
E
Finished in 0.004785 seconds.

  1) Error:
test_foo(AppTest):
NoMethodError: undefined method `closed?' for nil:NilClass
    /home/turnip/.rvm/rubies/ruby-1.8.7-p330/lib/ruby/1.8/net/http.rb:1069:in `begin_transport'
    /home/turnip/.rvm/gems/ruby-1.8.7-p330/gems/rack-proxy-0.3.4/lib/net_http_hacked.rb:50:in `begin_request_hacked'
    /home/turnip/.rvm/gems/ruby-1.8.7-p330/gems/rack-proxy-0.3.4/lib/rack/http_streaming_response.rb:52:in `response'
    /home/turnip/.rvm/gems/ruby-1.8.7-p330/gems/rack-proxy-0.3.4/lib/rack/http_streaming_response.rb:12:in `status'
    /home/turnip/.rvm/gems/ruby-1.8.7-p330/gems/rack-proxy-0.3.4/lib/rack/proxy.rb:45:in `perform_request'
    /home/turnip/.rvm/gems/ruby-1.8.7-p330/gems/rack-proxy-0.3.4/lib/rack/proxy.rb:11:in `call'
    /home/turnip/.rvm/gems/ruby-1.8.7-p330/gems/rack-test-0.5.7/lib/rack/mock_session.rb:30:in `request'
    /home/turnip/.rvm/gems/ruby-1.8.7-p330/gems/rack-test-0.5.7/lib/rack/test.rb:209:in `process_request'
    /home/turnip/.rvm/gems/ruby-1.8.7-p330/gems/rack-test-0.5.7/lib/rack/test.rb:57:in `get'
    rack_proxy.rb:22:in `test_foo'

1 tests, 0 assertions, 0 failures, 1 errors

rack_proxy.rb

require 'rack'
require 'test/unit'
require 'rack/proxy'
require 'rack/test'
require 'fakeweb'

class App < Rack::Proxy
  def rewrite_env(env)
    env["HTTP_HOST"] = "example.com"
    env
  end
end

class AppTest < Test::Unit::TestCase
  include Rack::Test::Methods

  def app
    App.new
  end

  def test_foo
    get "/"
  end
end