How can I make my Lab stop eating cat poo?

Hi, I've got a 5 year old lab who recently has picked up a very bad habit... after one of my cat's takes a dump, he goes into the cats bathroom and eats there poo! Trust me, I clean the cat box literally 3 times a day, but I have 6 cats so sometimes I don't even know a cat has used the restroom until I hear my lab open the door to the room where the cat's little box is... Every time I catch him doing it I make it clear that he is not supposed to go in that room! I can tell when he has done it even before I see the door open because he has that guilty look on his face lol so I know he knows that he is not supposed to do it, but he won't stop! It's like he knows when a cat is in there and will follow right behind them... a baby gate doesn't work because he will just push if over of hop over it... any solutions to this issue? Thanks and please, if your gonna be a rude know it all, please don't waist your time answering :-) I just want advice, not to be told what a terrible person I am by know it alls who don't even know me... Sorry, it just seams like every time I post a question in this section I end up regretting it because of rude a** holes...