Booster question

Hello,
I just bought a rebuilt dual diaphragm booster. Before installing it, I occurred to me to suck from the check valve and I'm not feeling any resistance. It feels as is there is an unlimited amount of air inside. Does this mean the booster is defective, or does it need a certain vacuum level before it seals?
Thanks.

Did you ever install this?

Yes, it gave my engine a massive vacuum leak.