Specifying a named scope in a mixin?

I would like to specify a named scope in a Module, to keep DRY. Example:

class Article < < ActiveRecord::Base

  include ReferenceData

  # ... end

module ReferenceData

  def self.included(base)     base.extend(ClassMethods)   end

  module ClassMethods

    named_scope :released, :conditions => {:is_released => true}



This does not work:


NoMethodError: undefined method `named_scope' for ReferenceData::ClassMethods:Module

Do you know how to specify my named scope inside a mixin module? Thanks a lot, Ewald