Nintendo does not want anyone to put the gaming system’s tiny cartridges in their mouths and reportedly taken measures to prevent that from happening.

Jeff Gerstmann, the co-founder of the video game blog Giant Bomb, tweeted that he put one of the cartridges in his mouth and regretted the move instantly.

“I put that Switch cart in my mouth and I'm not sure what those things are made of but I can still taste it. Do not try this at home,” Gerstmann tweeted last week ahead of Friday’s worldwide Nintendo Switch release.

But why do the cartridges taste so awful? Apparently, it’s coated with a material that is purposely meant to keep gamers – bloggers and kids alike – from putting the object in their mouths.

“A bittering agent (Denatonium Benzoate) has also been applied to the game card,” a Nintendo spokesperson told the website Polygon. The spokesperson added that Nintendo recommends keeping the cartridges from children.

The agent that the company uses is the “most-bitter chemical compound known to humanity,” according to Polygon. It’s commonly used to keep people from ingesting things they are not supposed to.