Finding out the gendee

My husband and I are trying to conceive our last baby. We already have three boys and we only want one more. I don't want to find out the gender and he does. I didnt want to find out with our last baby either but we did because we were moving and wanted to prepare. How would you handle this situation? If he finds out he will accidentally blab it before the baby is born. I don't know what to do! I really want a surprise.