Afraid to reveal the gender to my father

My father was disappointed when he found out I was a girl and again when he found out my sister was also a girl. Now that I'm expecting, he only keeps talking as if I'm having a boy. We don't know yet! We will find out in two days. And we'll be happy no matter what we're having. But I'm afraid to disappoint my father again! I even cried yesterday feeling afraid he wouldn't be excited about his first grandchild. Anyone has experienced the same situation?