I don't think it's martingale what I'm suggesting. Most likely it's a hole in the odds calculation system of two online casinos. It works only at these two and I've tried it in more than 10 casinos. However you cannot exploit it to win a lot, for some reason when I keep on playing after I've doubled my initial funds I lose it all.
It has nothing to do with martingale, I do not double the bet each time I lose a deal.