Activist investor Bill Ackman has built a new position in Warren Buffett’s Berkshire Hathaway Inc., according to a regulatory filing.

The billionaire said that his Pershing Square Capital Management Inc. held 3.51 million of the company’s Class B shares as of June 30, a stake valued at about $687 million based on Wednesday’s closing price. Ackman’s position in the company isn’t expected to be an active one, said a person familiar with the matter who asked not to be identified because the firm’s strategy wasn’t public.

Berkshire’s Class B shares, which have fallen 2.8% in the past year, rose about 0.3% after Pershing’s disclosure Wednesday.

Buffett isn’t seeing much value in stocks right now, which has led to a record US$122 billion cash hoard for his company. Berkshire sold $1 billion more worth of stocks than it bought last quarter, its biggest net selling since the end of 2017.

Buffett’s company spent the second quarter trimming its bet on Charter Communications Inc., cutting that stake by 5%. Berkshire ended up boosting its holding in Inc. during that period, although the US$1 billion Amazon holding is dwarfed by Berkshire’s more than US$49 billion bet on Apple Inc.

Acquisition Hiatus

He hasn’t had made a major acquisition in several years. He’s also pulled back on one of his newer ways to deploy cash, slowing down repurchases of Berkshire’s own stock in the second quarter.

Buffett’s assistant didn’t immediately respond to a message seeking comment on Pershing’s disclosure.

Ackman said this month that he had sold his stakes in United Technologies Corp. and Automatic Data Processing Inc. and had built a new position in an undisclosed company.

He opposed United Technologies’ proposed takeover of Raytheon Co. but chose to exit the stock rather than fight the deal, people familiar with the matter said this month. At ADP, Ackman sold his stock after earning a 50% return for his co-investors under the belief that much of the easy work to improve the payroll company’s operations had been done, they said.

ADP was Ackman’s last high-profile proxy fight. After several setbacks, including his losing bets on Valeant Pharmaceuticals International Ltd. and Herbalife Ltd., Ackman was forced to rethink his approach after a flurry of investor redemptions.

Ackman’s Returns

Since then, Ackman has stepped back from the limelight and put a renewed focus on his investment strategy. Pershing Square’s investments have returned about 48% this year through Aug. 6, according to its website.

Berkshire’s operating earnings fell in the second quarter as underwriting income at its insurers fell almost 63% to US$353 million, it reported this month. Its auto insurer Geico saw a jump in the average severity of its claims while the reinsurance unit swung to a pretax loss.