Boyfriends upset about the gender of our baby?

This is so immature but I think my boyfriend’s actually upset that we’re going to have a little boy.
Ever since I told him today, he hasn’t really been speaking and before I told him he was all happy and jolly.
Now he’s withdrawing and in a bad mood all day.
He is even yelling at me over small things.
Is it normal for him to be upset over the gender?
Boyfriends upset about the gender of our baby?
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