Twitter co-founder Evan “Ev” Williams is stepping down from the company’s board, Twitter announced in a SEC filing Friday afternoon. Williams will depart from the board at the end of this month, according to the filing.

“It’s been an incredible 13 years, and I’m proud of what Twitter has accomplished during my time with the company,” Williams said in a statement. “I will continue rooting for the team as I focus my time on other projects.”

Williams co-founded Twitter in 2006, and briefly led the company as its CEO from 2008 to 2010. More recently, he has been helming the publishing platform Medium.com.

Fellow co-founder and current CEO Jack Dorsey thanked Williams for his work Friday, saying that the company was “going to miss your voice in our board conversations.”

The departure doesn’t come as a complete surprise to anyone who has closely followed the company’s financials. Williams has been divesting much of his Twitter ownership recently, selling off around 8 million shares over the last three months alone, according to SEC filings.

Williams owned 29 million Twitter shares in April of 2018. By February of 2019, that number was down to around 11 million. This means that he now owns just around 1.5% of the company, based on outstanding shares, as opposed to 3.86% he held back in April of 2018.

Williams’ term on Twitter’s board was set to expire in 2021.