gistfile1.rb

    def create_scopes(klass, attribute_name)
      klass.enumeration.keys.each do |option|
        if respond_to? :scope
          scope option, where(attribute_name => klass.enumeration[option].first)
        end
      end
    end

Try:

scope option, lambda { where(attribute_name => klass.enumeration[option].first) }