before_validation_on_create

[adamsalter]

lib/active_record/acts/list.rb:67

http://github.com/rails/acts_as_list/blob/master/lib/active_record/acts/list.rb#L67

should be 'before_validation_on_create' since 'before_create' comes after validations, which means you can't have validations on the value of 'position'.