Sen. Bernie Sanders (I-Vt.) set Twitter alight with his tongue-in-cheek suggestion about using a lie detector on President Donald Trump during the 2020 presidential election debates.

Sanders’ joke came during a televised CNN town hall event hosted by Wolf Blitzer on Monday night. Blitzer asked Sanders how he would engage with Trump, if he was the Democratic nominee, on the debate stage.

Sanders, who confirmed his presidential run last week, replied: “Well, we’ll bring a lie detector along and every time he lies it goes ‘beep.’”