In a sign of doubt for the financial future of the superstore, billionaire investor Warren Buffett’s conglomerate Berkshire Hathaway dropped 89 percent of its shares in Wal-Mart Stores Inc. (WMT), worth $900 million, over the fourth quarter of 2016.

In a Securities and Exchange Commission filing, the firm listed holdings of fewer than 1.4 million shares of Wal-Mart, worth about $96 million—down from more than 55.2 million shares, worth $3.7 billion, in the first quarter.

Wal-Mart’s share price has dwindled over the past six months, from a high of more than $74 in August to $68.69 as of Thursday morning.

The Omaha, Nebraska-based Berkshire Hathaway, meanwhile, bumped up its holdings of Apple Inc. (AAPL), to 57.4 million shares, worth more than $7.7 billion, from 15.2 million shares in the third quarter. The tech giant, headed by chief executive Tim Cook and headquartered in Cupertino, California, has seen its share value climb steadily over the past six months, to $135.51 as of Thursday morning from around $109 in August. The increased stake in Steve Jobs' brainchild placed Buffett’s firm among Apple’s 10 biggest investors, according to Reuters.

Berkshire also boosted its shares of U.S.-based air carriers to $9.3 billion, with at least $2 billion worth of holdings in American Airlines Group Inc. (AAL), Delta Air Lines Inc. (DAL), Southwest Airlines Co. (LUV) and United Continental Holdings Inc. (UAL), respectively. All four companies have seen generous increases in their share values over the previous six months.

Buffet’s company, which he took over in the mid-1960s, also increased its holdings in the satellite radio maker Sirius XM Holdings Inc. (SIRI) and biotech and food manufacturer Monsanto Company (MON). The latter's shares have risen amid Sept. 14 news that its rival, German giant Bayer AG, would buy it for $66 billion.

Still, for all his billions in apparent investment foresight—Buffett, 86, has an estimated net worth of $75.1 billion—the Omaha native has been a critic of the belief that brokers can outperform indexes like the S&P 500. He has also suggested that managers are overpaid for their educated guesses. In an annual letter set for publication Feb. 25, Buffett was expected to further denounce the lucrative nature of speculation and stock-picking.