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Twitter co-founder and current board member Ev Williams is going to offload some of his Twitter stock.

Williams, who was once Twitter’s CEO and is the company’s largest individual shareholder, said Thursday that he plans to sell a “minority of my TWTR” stock over the next year. A Twitter spokesperson said that he doesn’t plan to sell “more than 30 percent” of his holdings.

Williams was careful to say the sale was for “personal” reasons, not company performance reasons. Twitter’s stock is down more than 15 percent over the past three months.

Williams explained the sale in a blog post, and wrote that he has spent a lot of money investing through his venture fund, Obvious Ventures, and also donated a lot to charity and political campaigns over the past year. “I’d like to continue,” he added.

Williams sold about $4 million in stock this week, according to an SEC filing, and has set up a 10b5-1 trading plan, which means he’ll sell at pre-determined dates moving forward to avoid any concerns over insider trading.

Here’s a statement from Twitter about Williams’s decision:

Evan Williams recently entered into a pre-arranged 10b5-1 stock trading plan as part of his continued efforts to diversify his financial positions and focus on his charitable organization and other endeavors. Ev, a co-founder of Twitter and member of the Board since 2007, has been a champion of Twitter since Day 1 and intends to maintain a significant ownership position in the company. The plan is not expected to result in the sale of more than 30% of Ev’s holdings.

Williams plans to stay on Twitter’s board, according to a spokesperson. Business Insider first reported on the sale.

Twitter stock was down less than 1 percent early Thursday following this news, so investors don’t seem worried, but this could still have an impact on Twitter’s future.

Twitter has long been seen as a possible target for an activist investor; the company’s single-class stock structure makes it vulnerable to an outsider with a big wallet who could come in and start buying shares (and thus, votes).

As the largest shareholder and a board member, Williams would certainly be influential in that kind of scenario. Selling off stock minimizes his overall say in how Twitter is run.

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