Active Scaffold and Inheritance

Had a problem getting two cases of single table inheritance to work in ActiveScaffold so thought I'd document it. Package and Classifier are the ActiveRecord classes.

class ExpressSchema 
  has_many :express_entities, :foreign_key => 'package_id'
end

class ExpressEntity 
  belongs_to :express_schema, :class_name => 'ExpressSchema', 
        :foreign_key => 'package_id'
end