Musk shed light on his bitcoin ownership in response to a question from a Twitter follower asking why there were so many bots impersonating him to push cryptocurrency scams.

“What’s with all the ETH spam?” the Twitter user asked, referring to the cryptocurrency Ethereum. Musk tweeted back: “Not sure. I let Jack know, but it’s still going.” Musk was referring to Twitter CEO Jack Dorsey.

“I literally own zero cryptocurrency, apart from .25 BTC that a friend sent me many years ago,” Musk said in a tweet on Thursday. That’s about $2,500 as of Friday evening (as of Friday afternoon, one Bitcoin was worth $10,012).

Not sure. I let @jack know, but it’s still going. I literally own zero cryptocurrency, apart from .25 BTC that a friend sent me many years ago.

— Elon Musk (@elonmusk) February 22, 2018

That’s not a lot of money for Musk, who is worth billions. But even if Musk needed to access his bitcoin, he’d be unable to.

Late last year, a theory circulated that the true identity of Satoshi Nakamoto, Bitcoin’s pseudonymous creator, is Musk. The blog post that floated the idea was by Sahil Gupta, a former intern at Musk’s other company, SpaceX.

Not true. A friend sent me part of a BTC a few years, but I don’t know where it is.

— Elon Musk (@elonmusk) November 28, 2017

Someone on Twitter sent Musk a news article about the post. Not only was it untrue, Musk said, but he’s forgotten where his bitcoin is stored. Losing bitcoin isn’t so unusual. As Fortune exclusively revealed, somewhere between 2.78 million and 3.79 million bitcoins have been misplaced over the years.