UTF-8 routes.rb and Passenger vs. Mongrel/WEBrick

My (Rails 3) routes.rb has the following entry:

   resources :articles, :path => "記事"

This works in my production environment, as passenger unescapes the
path from /%E8%A8%98%E4%BA%8B to /記事.

However, in my development environment, I'm using Mongrel, which does
not unescape the path, so it does not work unless I change my routes
to

   resources :articles, :path => Rack::Utils.escape("記事")

I'm trying to figure out which component has the bug. Any
suggestions?