As Facebook stock plunged over 20% in after-hours trading Wednesday following a disappointing earnings report, CEO Zuckerberg lost $17.6 billion in net worth.

The 34-year-old Facebook billionaire, who had been worth as much as $86.5 billion when Facebook stock traded at an all-time high earlier in the day, now has a net worth of about $68.9 billion, based on regulatory filings with the U.S. Securities and Exchange Commission. That figure includes some $2.7 billion in cash and real estate, according to Bloomberg’s Billionaire index.

That places Zuckerberg, who had been the world’s third-richest person, at No. 6, below billionaires including Berkshire Hathaway’s Warren Buffett, French business magnate Bernard Arnault, and Zara founder Amancio Ortega.

Zuckerberg’s net worth had surpassed Buffett’s in June as shares of Facebook continued to climb and Buffett continued to give much of his wealth away in charitable donations. (Today, Buffett is worth roughly about $82.3 billion.)

Facebook’s founder is the media company’s largest shareholder, with 12.8% of its shares outstanding.

Zuckerberg’s paper losses come after Facebook revealed mixed earnings and slowing growth during the second quarter of 2018. During the quarter, the company added 22 million daily active users, lower than the 41 million it added in the same quarter a year earlier. Chief financial officer David Wehner told analysts in a follow-up call to brace for a possibly deeper slowdown as the company seeks to expand new offerings such as Stories and increase privacy and security for users.