Slack founder and CEO Stewart Butterfield accepted an award at The Wall Street Journal's 2015 Innovator Awards ceremony on Wednesday evening at New York City's Museum of Modern Art. But his speech wasn't well received by at least one of the other stars in the room.

Robert De Niro at Wednesday night's WSJ. Magazine 2015 Innovator Awards. (Photo by Dimitrios Kambouris/Getty Images for WSJ. Magazine 2015 Innovator Awards) During his speech, Butterfield quipped that he was a long way from San Francisco and that among the stylish crowd of actors and models, he was clearly receiving the "nerd award."

According to Page Six, Butterfield then singled out actor Robert De Niro and said, "I watched 'Godfather II' on the plane ... When you killed Don Fanucci, I liked that."

De Niro, who most recently starred in "The Intern" alongside Anne Hathaway, didn't seem to know who Butterfield was. And apparently didn't think the tech founder was funny.

"Whoever the last speaker was ... I thought you were a bit condescending to us actors ... celebrities," Page Six quotes De Niro as saying. "I'm gonna go on record with you just to say that. And I don't give a f--- who you are."

Slack, the work-communications program that Butterfield founded, has been valued at $2.8 billion by investors.

Butterfield later tweeted a photo of De Niro and wrote, "I literally got trash-talked by Robert De Niro ... #lifegoals."