Even tech moguls make mistakes online.

Elon Musk committed a bit of a Twitter blunder late Tuesday. The billionaire inventor and CEO of Tesla  and SpaceX  was trying to get in touch with John Carmack, the chief technology officer at Oculus, Facebook’s virtual reality project. But instead of sending a private message, Musk tweeted directly at Carmack, so his 16.7 million followers could see it, Business Insider reports.

“Do you have a sec to talk? My cell is…” the tweet read before listing a phone number. Musk’s tweet was quickly deleted, but not before several followers noticed.

CNBC rang the number Musk posted and discovered a recorded message from the video game God of War. The audio clip, recorded by game creator David Jaffe, is one of two secret codes hidden in the game. “By the Gods you’ve done it,” the message says. “Somehow you’ve found your way here to me. I offer you my congratulations and my respect.”

You can hear the message yourself here, but probably not on Musk’s phone anytime soon — he’ll likely be changing that number.