Brake Booster issue?

I have a 1964 barracuda. I just installed front disc scarebird kit. rear are factory drum. I installed new M/C and booster. I haven't done a road test yet. I've started the car a I shut it off and hear air escaping from the booster area. My question is should I install an in-line check valve on the hose coming from the carb to booster? or am I missing something else.

Thanks