The crackdown on free thought continues at the Democratic National Convention.

Arkansas delegate Frank Klein says he was stripped of his credentials after he held up an “unauthorized sign” during President Obama’s speech to the DNC Wednesday night.

Klein, a Fourth Congressional District delegate for Bernie Sanders, claims he held up a “Stop TPP” sign, which was allegedly against the rules.

“I’ve been denied my credentials because I refused to follow DNC rules,” Klein says, “and I held up an unauthorized sign the DNC said wasn’t authorized.”

The sign read “Stop TPP,” according to the Sanders delegate.

“They refuse to issue my credential to me, which I constitutionally should be able to get,” he says.

Will the DNC replace him with a paid seat filler?

UPDATE: Here’s a tweet showing a delegate with an “unapproved” sign being photographed for potential expulsion: