OMAHA, Neb. (AP) — Billionaire Warren Buffett says stocks remain the best option for investors — not bonds, and especially not bitcoins. Buffett says he doesn’t think the stock market is overpriced compared with other options even though he’s had trouble finding entire businesses to buy at reasonable prices. Buffett appeared on CNBC Monday after spending Saturday answering questions before thousands of shareholders.

Buffett says cryptocurrencies like bitcoin are nonproductive assets similar to gold. So Buffett says anyone buying bitcoin is betting that someone else will pay more for it later. Buffett reiterated his standard advice that buying an index fund, such as the S&P 500 fund, regularly over time is the best option for most people. Roughly 40,000 people attended Berkshire Hathaway’s annual meeting on Saturday.