Probing or popping is the only way to know for sure. Very few snakes can be sexed with high percentage accuracy from looking at the tail/vent area.
But judging by the tail, I'd guess male as well. Also males will stay very small compared to females(ty Rafal). When he's full grown in a year or two at under 20 inches and less than 200 grams, you'll know for sure if you don't probe or pop. Females get 2ice that size.

Maybe Rafal wil chime in casue I think he may love/appreciate african house snakes more than me and he has much more knowledge of them than I do.