Jack Ma is preparing one of his biggest Alibaba Group Holding Ltd. stake reductions in recent years, and the timing could hardly be worse.

The wealth of the e-commerce giant’s co-founder shrank by $683 million after Alibaba’s biggest selloff in more than a year Thursday, just days before Ma’s planned share sale next week.

Alibaba’s stock tumbled after the company reversed plans to spin off and list its $11 billion cloud business unit in a strategy reset. The move, spurred by increased US restrictions on chip sales to China, sent shares of the company plummeting 9% in New York trading.

Ma’s net worth slid to $29.2 billion, according to the Bloomberg Billionaires Index, while the company’s chairman Joseph Tsai took a hit of about $261 million.

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The 59-year-old Ma had earlier disclosed plans to sell 10 million shares worth about $870 million on Nov. 21, according to regulatory filings Thursday. JC Properties Ltd. and JSP Investment Ltd., two companies owned by Ma, will each sell 5 million shares, according to the filings.

Ma, who relinquished all his roles in Alibaba in 2020, has been selling shares in recent years and his stake in the business has dropped below 5%.

--With assistance from Edwin Chan.