Fuel leaking when shut off valve is closed

[zaugger]

Hey folks...still a newbie here. I replaced manifold gaskets yesterday. It went well, but when I came home from testing and turned the fuel off (as I usually do because the fuel in the bowl make my garage stink), tho motor dieseled on more than normal. Later in the evening my daughter notice the smell of gas and when I checked on it a significant amount of fuel was dripping from the carb. Need to fix that for sure, but I'm surprised it's happening with the fuel shot off. Is it as simple as a bad valve, or has anyone experienced this with a different explanation?

Thanks for your help!