Am I right to do this?

My boyfriend is planning to propose to me around Christmas and I’m really excited and I really want to marry him but we don’t live together right now (we will in may) and he’s currently living with these guys who smoke a lot of weed and because he’s in that environment he’s also smoking a lot of weed. I’m not against weed and I have it too sometimes but I’m getting really annoyed because he smokes it and gets high almost everyday and I really don’t want to marry someone who gets high everyday. I’m fine with it every now and then but he’s doing way too much. I want to tell him that I’m not going to marry him if he keeps getting high everyday and I want him to either choose weed or marrying me. But do you think I’m being really harsh? Should I just forget about it and let him do whatever he wants until we move in together or do you think I’m being fair and should say this to him?