Vacuum advance tube fitting fell out of carb! Advise?

Doing a general tune up, oil change, and tire rotate on my car this evening. 170 slant six with a Carter BBS. Checked the timing and when I disconnected the vacuum advance from the carb, I noticed the tube fitting felt loose. With a small amount of gentle persuasion I was able to pull it out with my fingers. Any recommendations on how to get that back in there, make it stay, and not leak vacuum?