The restaurant industry is a competitive place, but a few restaurateurs have figured out that they can keep customers coming back simply by adding addictive, illegal drugs to their dishes. Dropping a bit of an opiate into a dish might seem like a clever way to get customers hooked, but officials in China do not like that at all, as two restaurateurs recently discovered.

According to Shanghaiist, two completely different Shanghai restaurateurs have been caught adding Narceine, a mild relaxant found in opium, to crayfish. One of the restaurateurs was sentenced to three years and a half in prison and fined $8,064. The second restaurateur received a three-year sentence and fined $6,459.

Adding addictive substances to food might keep customers loyal, but it’s a good way to run afoul of the Shanghai Food and Drug Administration. Still, restaurants keep trying. Just last October, two restaurants in Guangzhou were caught adding addictive poppy powder to dishes to make them “especially aromatic and full of flavor.”