Spotify launched its audiobook business just last month with 300,000 titles, but is now saying that Apple is engaging in “anticompetitive” behavior that is impinging the new business, the company wrote in a blog post. It said that Apple rejected its audiobook purchasing system three times due to a violation of its rules. To comply, it had to hide the price of the audiobooks and do sales outside of the main app via an email link.

All of that makes it harder for Spotify to compete, as users can’t easily compare prices. “[This] harms not only consumers, but, this time, also authors and publishers who now find themselves under Apple’s thumb.” It’s also highly inconvenient for buyers used to simply clicking on a link to buy an audiobook.

Spotify’s audiobooks could have easily been accepted if the company had followed the App Store rules, Apple told The New York Times. “We provided them with clear guidance on how to resolve the issue, and approved their app after they made changes that brought it into compliance,” an Apple spokesperson said.

Spotify could also have sold its audiobooks through the App Store’s purchasing system, but Apple would then take a 30 percent cut — putting Spotify’s audiobooks at a considerable disadvantage against Apple Books. “With our Audiobooks launch, Apple has once again proven just how brazen it is willing to be with its App Store rules, constantly shifting the goalposts to disadvantage their competitors,” said Spotify CEO Daniel Ek.

Spotify is already in a battle with Apple over music subscriptions, having said that its 30 percent commission harms consumers. The European Commission issued Apple with a Statement of Objections after concluding that Apple was in possible breach of EU laws, but has yet to reveal a final verdict. “Almost four years. That’s how long it’s been since Spotify filed a complaint against Apple with the European Commission, and we are still waiting on a decision,” said Ek.