Today at an industry event, JPMorgan CEO Jamie Dimon didn’t mince words when it came to bitcoin. “It’s a fraud,” he said, adding that it “won’t end well,” reports Bloomberg .

Dimon said that he would fire any of his traders if they began trading bitcoin. “For two reasons,” he said, “It’s against our rules, and they’re stupid.”

It should be noted that Dimon has long been bearish on bitcoin, likely because JPMorgan, for years, has attempted to build digital currencies that would rival it. In 2013, the bank filed a patent for an electronic currency that bore a striking resemblance to bitcoin.

Dimon, however, isn’t the only figure warning about the bitcoin bubble; U.K. financial watchdog the Financial Conduct Authority issued a striking warning today to those investing in cryptocurrencies. It warned that doing so is extremely risky and investors should be prepared to lose all of the money they invested.

The market has reacted. Shortly after Dimon’s comments were made public, bitcoin prices dropped. The price peaked today at $4,368.22, and is currently at $4,101.49.

Bitcoin has been steadily rising over the last year. Although with Dimon not a fan, who’s to say what longevity the cryptocurrency will have.

Still, criticism hasn’t tempered the voracity of startups aimed at bringing more investors aboard, like the one some MIT grads started to let anyone invest in or start a bitcoin fund.