Dispute over finding out sex of baby

⚜️Kay⚜️
My husband wants to know the sex of the baby and I want to be surprised at delivery. I have a son and daughter already and I just want this one to be a surprise. Have any of you ever had this issue? I know it's not a common problem to have. 
Of course he could know the sex and I stay left in the dark but there's the possibility that he could have a slip of the tongue.