Mongrel2 rack handler won't daemonize

Question

I am trying to deploy an app with Mongrel2-rack-rails3 stack. I am using khi-rack-mongrel2 handler for ruby rack. The problem is that even if I setup everything for local development, I can't make rails server daemonize itself by running it with -d option. While starting without daemonization option I get following output:

% rails s Mongrel2
=> Booting Mongrel2
=> Rails 3.0.9 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server

The handler starts and I can make requests to my rails app. However If I start my server with -d option I get this:

% rails s Mongrel2 -d
=> Booting Mongrel2
=> Rails 3.0.9 application starting in development on http://0.0.0.0:3000

The handler starts, but does not daemonize itself. Can someone point me out to the issue at hand?

Here are the contents of my config.ru file:

require ::File.expand_path('../config/environment',  __FILE__)
Rack::Handler::Mongrel2.run(MyProject::Application,
  :recv => 'tcp://127.0.0.1:2050',
  :send => 'tcp://127.0.0.1:2051',
  :uuid => 'my_project'
)