new proportioning valve leaking

I'm swapping to disc brakes. I installed my new Inline Tube proportioning valve, connected all the lines, went to bleed the system and found fluid leaking out from the base of the hexagonal piece on top where the front brake line comes in from the master cylinder (see picture). Has anyone else had this problem? I tried tightening the hex part, but it seems pretty tight already.

Same thing happened with mine a few years ago. I found another crush washer and had to file it to size. Then my brake light stayed on all the time. An internet search revealed that it's a common problem. I guess Inline tube doesn't care that they sell a defective part.