Dear Michael: A‘head' of the curve

Dear Michael,

My boyfriend and I recently broke up and a new problem has come up. I bartend at a local bar, and the other night he came in with his friends. He and I were friendly, but he joked around with his friends a lot and was being very wise to me about our past relationship. I played it off like I didn't care, but it made me very uncomfortable. I'm afraid of this becoming a regular occurrence. If it happens again, what should I do to make him understand that it upsets me without looking like a fool in front of him and his friends?

Sincerely,

Ex Problems