Bill Gates questioned Elon Musk’s goals for Twitter, as well as what free speech would look like. Gates said Musk has a “mind blowing” track record with Tesla and SpaceX.

Bill Gates said he’s unsure what Twitter’s future will look like under Elon Musk’s guidance. Though the Microsoft founder expressed concern over how Musk may address misinformation on the social media platform, especially considering his emphasis on promoting “free speech.”

Last week, Musk said that he defines free speech as that which matches the law. Experts previously told Insider that Musk’s approach to free speech could lead to the further spread of misinformation and hate speech on Twitter.

In April, Musk appeared to mock Gates with a meme of the Microsoft founder alongside a pregnant man emoji. The meme was posted in response to a series of screenshots of texts that appeared to be between the two billionaires.