Well said @Big_Mama, I think open communication is important here. Talking about your fantasies with your partner is good for a relationship and helps uncover more about each other’s turn-ons, even if the original fantasy never quite happens the way they hoped! In the case of not being in to the fantasy @walk_on_walls, would you consider it as a way to talk about your own desires? Not necessarily a tit-for-tat exchange (half-hearted pun :p ) but at least a consideration that there are two of you in the relationship.
There’s certainly some vulnerability in sharing your fantasies, so I’d have to give him respect for sharing his. And you’re right @Kit, after he’s shared, it’s easier for me to share back and make the discussion more balanced.