Controller Module Problem

Am I missing something?

class Admin::MainController < ApplicationController before_filter :is_admin?, :except => [:login, :index, :authenticate]

#other stuff end

class Admin::ProductController < Admin::MainController

#more stuff end

When attempting to call a method in ProductController, I get the error/trace

NameError uninitialized constant MainController

c:/ruby/lib/ruby/gems/1.8/gems/activesupport- 1.3.1/lib/active_support/dependencies.rb:123:in const_missing' c:/ruby/lib/ruby/gems/1.8/gems/activesupport-1.3.1/lib/active_support/dependencies.rb:131:in const_missing’ c:/ruby/lib/ruby/gems/1.8/gems/activesupport- 1.3.1/lib/active_support/dependencies.rb:133:in `const_missing’ #{RAILS_ROOT}/app/controllers/admin/product_controller.rb:1 This error occured while loading the following files: ./script/…/config/…/app/controllers/admin/product_controller.rb

main_controller.rb

Am I missing something obvious?