A day after it was revealed he owned the largest stake in Twitter, slightly more than 9% of shares, Elon Musk has joined the company’s board of directors.

The Tesla and SpaceX founder will be on the board until at least 2024, according to a regulatory filing.

As a stipulation of his board membership, Musk won’t be allowed to own more than 14.9% of Twitter shares while on the board and for three months following a departure from the board.

After the announcement, Musk tweeted, “Looking forward to working with Parag & Twitter board to make significant improvements to Twitter in coming months!”

“I’m excited to share that we’re appointing @elonmusk to our board!” tweeted Twitter CEO Parag Agrawal. “Through conversations with Elon in recent weeks, it became clear to us that he would bring great value to our Board.”

“He’s both a passionate believer and intense critic of the service, which is exactly what we need on @Twitter, and in the boardroom, to make us stronger in the long-term. Welcome Elon!’

In recent weeks, Musk, who is an active Twitter user with upwards of 80 million followers, has questioned the platform’s commitment to free speech and the First Amendment of the U.S. Constitution.

He recently ran a poll on Twitter asking users if they felt the same. More than 2 million responded, with over 70% saying Twitter does not adhere to free speech.

Twitter stock has surged since Musk’s acquisition of about $3 billion worth of the company’s stock.

Some information in this report comes from The Associated Press.