United Auto Workers (UAW) President Shawn Fain invoked rapper Nelly at the Democratic National Convention (DNC) on Monday night while firing up a raucous crowd celebrating Vice President Harris’s nomination for the White House.

Fain, who said he was “honored” to endorse Harris and her running mate Minnesota Gov. Tim Walz, drew an energetic response from the crowd, who had gathered in Chicago on the first night of the four-day confab.

The union leader acknowledged the energy of the crowd with an unexpected pop culture reference.

“In the words of the great American poet Nelly: ‘It’s getting hot in here,’” Fain said to cheers.

“It’s hot in here. It’s hot in here because you’re fired up and fed up,” he said, adding: “The American working class is in a fight for our lives.”

Fain has long been outspoken critic of Harris’s Republican rival, Donald Trump, and the UAW endorsed Harris in July. The union released a video earlier this week slamming Trump as “all talk” on labor rights.

The UAW president echoed those remarks in his speech Monday night, arguing Harris was the best choice for the working class.

“Donald Trump laughs about firing workers who go on strike,” Fain said Monday night. “And Kamala Harris stands shoulder to shoulder with workers when they’re on strike.”

Harris and Walz met with UAW workers last week in Michigan. Trump, meanwhile, has bashed Fain repeatedly, calling him at one point a “stupid person.”

The UAW’s appearance at the convention comes as both parties look to make ground with working-class voters, especially in the Rust Belt states of Michigan, Pennsylvania and Wisconsin.