Rubber Check Valve in Sankey Tap

I bought the commercial to homebrew kegerator conversion kit and I have a question about connecting the CO2 side adapter to my old Sankey tap. The old setup had a rubber check valve that was inserted into the tap and also functioned as a washer. The kit only comes with a black neoprene washer, which is too big to fit in the recess on the tap. Should I stack the black neoprene washer on top of the rubber check valve as I’ve done in the photo or should I just use the rubber check valve only? I imagine that not using the check valve would be a bad thing.

Thanks!

I would use check valve as well as washer.