ActiveRecord 3.0.9 error -- has_one :through a has_one with :conditions

app_models_asset.rb

class Asset < ActiveRecord::Base
  has_many :ownerships
  has_many :owners, :through => :ownerships
  has_one :current_ownership, :class_name => Ownership.name, :conditions => { :current => true }
  has_one :current_owner, :through => :current_ownership, :source => :owner
end

rails console

Asset.joins(:current_owner).all

ActiveRecord::StatementInvalid: Mysql2::Error: Unknown column 'owners.current' in 'on clause': SELECT `assets`.* FROM `assets` INNER JOIN `ownerships` ON `assets`.`id` = `ownerships`.`asset_id` INNER JOIN `owners` ON `owners`.`current` = 1