A noted investor is taking aim at bitcoin and cryptocurrencies, deeming them in a recent investor note as “not real”.

Howard Marks is the co-chairman of Oaktree Capital, which according to its website reported $99 billion in assets under management as of last month. His comments come amid growing chatter amongst Wall Street analysts including those from Goldman Sachs and Bank of America, to name a few.

Yet Marks – who according to CNBC gained notoriety for his prescient calls about both the dot-com bubble and the financial panic of the late 2000s – took a decidedly negative tack in a new memo earlier this week. Branding cryptocurrencies as “an unfounded fad,” he compared it to those previous episodes, as well as other economic situations like the South Sea Bubble from the 1700s.

He wrote:

“In my view, digital currencies are nothing but an unfounded fad (or perhaps even a pyramid scheme), based on a willingness to ascribe value to something that has little or non beyond what people will pay for it. But this isn’t the first time. The same description can be applied to the Tulip mania that peaked in 1637, the South Sea Bubble (1720) and the Internet Bubble (1999-2000).”

Questioning whether bitcoin’s use for payments qualifies it as money, Marks goes on to raise doubt about the market’s prospects should the prevailing optimism among speculators start to diminish.

“What will happen to bitcoin’s price and liquidity in a crisis if people decide they’d rather hold dollars (or gold)?” he asked.

Later, Marks places the recent developments around cryptocurrencies in the wider context of the international market, including historically low yields on bonds and “some of the highest equity valuations in history”.

He goes on to state that he’s not saying that “digital currencies are sure to end up worthless” or that stock prices are too high today – rather, that the market today, in his view, is in a precarious state.

“Not a nonsensical bubble – just high and therefore risky,” he notes.

Image via Oaktree Capital/YouTube