Bernie Sanders and Donald Trump used late-night TV appearances this week to hype a potential debate between them. So with the event now dead, it was only fitting that Sanders would return to late night on Friday to knock Trump for backing out.

Groaning and shaking his fists in frustration, the senator from Vermont told HBO’s Bill Maher he “would have loved to” debate the presumptive Republican presidential nominee before the California primary on June 7.

“First he said he would do it,” Sanders said. “Then he said he wouldn’t do it. Then he said he would do it. Then he said he wouldn’t do it. So I would hope that if he changed his mind four times in two days, (he’d) change it a fifth time. You know, Trump claims to be a real tough guy, pushes people around. Hey, Donald, come on up. Let’s have a debate about the future of America.”

As recently as Thursday, Trump said he would be willing to face off against Sanders if either the Democratic underdog’s campaign or a network sponsor would pony up between $10 million and $15 million to benefit what he vaguely described as “women’s health issues.”

That was after telling ABC’s Jimmy Kimmel on Wednesday that he’d be game for a debate. Sanders told Kimmel the same thing.

But on Friday, before Sanders’ interview with Maher, Trump reversed course.

“Based on the fact that the Democratic nominating process is totally rigged and crooked, Hillary Clinton and Deborah Wasserman Schultz will not allow Bernie Sanders to win, and now that I am the presumptive Republican nominee, it seems inappropriate that I would debate the second-place finisher,” he said in a statement.

Maher, a Sanders supporter, piled on.

“Mr. Macho chickened out,” he declared.

Sanders and Maher discussed other subjects, too, including a report this week by the State Department inspector general that criticized Clinton for her private email use as secretary of state. Sanders has consistently declined to hammer the likely Democratic nominee for a practice that even Clinton acknowledged was a “mistake.” Maher seemed to wonder whether Sanders would go on the attack, now that “the story has moved a little bit.”

Sanders still refused to attack.

“There is enormous frustration on the part of the American people with the way we do politics in this country,” he said. “And what most politicians do is say, ‘I’m great; you’re terrible. Vote for me; the other guys are scum of the earth. Blah, blah, blah, blah.’ But, you know what? People are hurting in this country. Our middle class is disappearing. We’ve got a lot of poverty. We don’t have health care for all people. People want us to talk about their lives and their issues and not just spend our whole lives attacking our opponents.”