Elon Musk may be joining Twitter’s board, but some employees are apprehensive about the potential implications.

The Tesla CEO has been an avid user, and critic, of Twitter, with his tweets sparking spirited discussion on a variety of topics. Musk has been a vocal advocate for change, wanting an edit button and more unrestricted free speech.

According to Reuters, four different Twitter employees spoke to the outlet to voice concerns that Musk’s arrival could lead to a reversal, or at least a weakening, of years of work by the social media company. Twitter’s goal has been to sponsor healthy, safe discourse, and it has repeatedly taken action to suspend or ban users who violate those policies.

Twitter employees are also concerned about Musk’s history of using the platform to attack people he disagrees with, a pattern of behavior he has come under fire for on more than one occasion.

Twitter has tried to reassure people that its development and policies are not dictated by the board of directors, but some employees are not convinced.

“I find it hard to believe (the board) doesn’t have influence,” said one employee. “If that’s the case, why would Elon want a board seat?”