The so-called Oracle of Omaha has become the latest high-profile investor to weigh in on bitcoin - as he gave an indication of his succession plans by promoting two potential heirs.
Warren Buffett, the cherry Coke-swilling boss of investor Berkshire Hathaway, said "with almost certainty" that cryptocurrencies "will come to a bad ending".
During an interview with CNBC, he added: "When it happens or how or anything else, I don't know."
The self-made billionaire's comments came after he labelled bitcoin a "mirage" and a joke back in 2014.
Buffett also refused to jump on board with bitcoin futures, despite talk of the contracts, which were launched by two US exchanges in December, adding an air of respectability to the crypto craze. Bitcoin futures are expected to attract a greater number of institutional investors this year.
"I get into enough trouble with things I think I know something about. Why in the world should I take a long or short position in something I don't know anything about?" he asked.
"We don't own any, we're not short, we'll not grab a position in them."
Many investors are turning their attention to bitcoin and its rivals such as Ripple, Ethereum and Litecoin. Cryptocurrencies have already paid off for some of Buffett's younger rivals, including early adopters such as the Winklevoss twins and veteran Silicon Valley venture investor Tim Draper.
But opinion has been split, with some steering clear of what's been described as a bubble, while regulators have warned investors they could lose everything.
Yesterday JP Morgan boss Jamie Dimon u-turned on his previous assertion it was a "fraud".
Meanwhile the 87-year-old oracle of Omaha promoted two long-serving potential heirs to the Berkshire Hathaway throne, Gregory Abel and Ajit Jain, to vice chairs with board positions. There has long been speculation as to who will succeed Buffett, and when it will happen.
He revealed a successor had been identified back in 2015, but has remained tight-lipped as to who it is.
Buffett, who is one of Apple's biggest investors but does not own an iPhone, said the appointments were "part of a movement to succession over time" and Abel and Jain were "the two key figures".
Berkshire Hathaway's famously valuable class A shares were 0.9 per cent higher at pixel time, at $307,170.