What is the ruling for someone who forgot to make up missed fasts (qada') and then Ramadan began?

The jurists agreed that forgetfulness is an excuse that removes sin and accountability, but it does not waive the obligation to make up for missed Ramadan fasts if the next Ramadan begins. They differed regarding the obligation of expiation (fidyah) along with making up the fasts, holding two opinions: The first, which is the stronger opinion, is that expiation is not obligatory, as forgetfulness is an excuse that removes both sin and expiation. The second opinion is that expiation is obligatory, and forgetfulness only removes the sin.