Reference a constructor argument from a trait

In Scala, is it possible for a trait to reference a named constructor argument of the class it is mixed into? The code below doesn't compile because ModuleDao's constructor argument is not a val as defined in the trait. If I add val before the constructor argument to make it public, it matches up with the one in the trait and it compiles, but I'd prefer not to set it as a val.

trait Daoisms {
  val sessionFactory:SessionFactory
  protected def session = sessionFactory.getCurrentSession
}

class ModuleDao(sessionFactory:SessionFactory) extends Daoisms {
  def save(module:Module) = session.saveOrUpdate(module)
}

/* Compiler error:
class ModuleDao needs to be abstract, since value sessionFactory in trait Daoisms of type org.hibernate.SessionFactory is not defined */

// This works though
// class ModuleDao(val sessionFactory:SessionFactory) extends Daoisms { ... }