Rmagick doesn't work

I've encountered a really strange problem with the latest Rails master. Anything that involves RMagick gem will run OK on the first request and generate 'uninitialized constant' error on all subsequent requests, until you restart WEBrick. Try running the attached app and just refresh the page. I didn't have this problem 2 days ago. I'm using Ruby 1.9.2dev on Ubuntu Linux 10.04.

Error:

ActionController::RoutingError (uninitialized constant RmagicController::Magick):
  app/controllers/rmagic_controller.rb:4:in `<class:RmagicController>'
  app/controllers/rmagic_controller.rb:1:in `<top (required)>'

rmagic_controller.rb:

class RmagicController < ApplicationController

  require 'RMagick'
  include Magick

  def index
    img = Magick::Image.read(File.join(Rails.public_path, 'images/test.jpg')).first
    send_data(img.to_blob, { :type => 'image/jpeg', :disposition => "inline" })
  end
end