SearchLogic problem with left join in order SOLVED!

item.rb

class Item < ActiveRecord::Base

  named_scope :ascend_by_optional_category_title, 
                        :joins => "LEFT JOIN categories AS optional_categories ON optional_categories.id=items.category_id",
                        :order => "optional_categories.title"

  named_scope :descend_by_optional_category_title, 
                        :joins => "LEFT JOIN categories AS optional_categories ON optional_categories.id=items.category_id",
                        :order => "optional_categories.title DESC"

end

searchlogic.rb

Item.search( :order => :ascend_by_optional_category_title )