Elon Musk has criticized Apple’s App Store policies amid claims the company “threatened to withhold” Twitter from its store, according to Musk.

In subsequent tweets, Musk spoke out against Apple’s 30 percent “tax” on in-app purchases and said the owner of the App Store censors other developers. He also said that Apple has “mostly stopped advertising on Twitter” (Apple is not the first major advertiser to do this is in recent weeks).

This isn’t the first time Apple has had trouble with Twitter. In a recently published article by The New York Times, Twitter’s former head of trust and safety, Yoel Roth, said Apple’s App Store reviewers often flagged content on Twitter during the app review process.

“In my time at Twitter, representatives of the app stores regularly raised concerns about content available on our platform,” Roth wrote, saying that app reviewers had flagged instances of racial slurs and nudity on the service. “Even as they appear to be driven largely by manual checks and anecdotes, these review procedures have the power to derail company plans and trigger all-hands-on-deck crises for weeks or months at a time.”

Musk did not specify whether Apple is withholding new updates to the service or threatening to remove the app from its store altogether. However, there are a number of issues that may guarantee further scrutiny of Twitter.

Last Sunday, The Guardian reported that Twitter initially failed to remove a newly uploaded video of a 2019 Christchurch, New Zealand, terrorist attack until government officials alerted the company to its existence. Activists also express widespread concern about the rise of hate speech and restoring accounts of famous people who had been banned for violating Twitter’s hate speech policy.

Apple has strict, though unevenly applied, rules governing the content that can appear in apps in its store. Parler, Twitter’s free speech competitor, was  removed from the App Store for several months due to lax content moderation policies (the app was reinstated after it deployed an AI-based moderation system). In 2018, Tumblr banned adult content after a brief removal from the App Store.