Former President Bill Clinton cracked a joke about Donald Trump’s recent obsession with a certain fictional cannibal during his speech at the Democratic National Convention on Wednesday night.

Trump has been invoking “the late, great, Hannibal Lecter” when invoking conspiracies around immigration and crime. The former president has likened migrants to the “Silence of the Lambs” character, pushing the conspiracy theory that other countries are sending “bloodthirsty terrorists, savage gang members, and child predators” to the border “to prey on our people, to prey on you, to prey on everybody.”

The reference has become a trope in his speeches. But its meaning remains unclear, and Clinton took the opportunity to poke fun at it.

“When you send a signal to the other countries, you want them to know, whether they agree with you or not, at least that you’re on the level,” he told the audience. “What are they supposed to make of these endless tributes to the ‘late, great Hannibal Lecter’?”

“President Obama once gave me the great honor of saying I was ‘the explainer in chief,’” he added. “Folks, I’ve thought and thought about it, and I don’t know what to say.”