Warren Buffett said he’s no fan of cryptocurrencies like bitcoin and is confident that the run up in their value is fleeting.

“In terms of cryptocurrencies, generally, I can say almost with certainty that they will come to a bad ending,” Buffett said in an interview on CNBC on Wednesday. “Now when it happens, or how or anything else, I don’t know. But I know this: If I could buy a five year put on every one of the cryptocurrencies, I’d be glad to do it but I would never short a dime’s worth.”