Elon Musk is taking aim at Apple Inc.

The Tesla CEO hit up Twitter on Friday to slam the tech giant over its App Store fees, referring to them as a “de facto global tax on the internet.” Musk concluded his post by expressing his support for Epic Games, the software developer that is suing Apple over its controversial App Store policies.

Epic Games filed a lawsuit against Apple in August 2020, when its wildly popular game Fortnite was remove from the App Store. Apple made the move after Epic offered players a 20 percent discount on the in-game currency known as “V Bucks”; however, to take advantage of the savings, players had to purchase the currency directly from Epic, rather than going through Apple. 

Epic accused Apple of running a monopoly through its in-app purchase system, which gives Apple a 15-30 percent cut of all sales made within the apps. Musk went on to admit that he likes and uses Apple products, but said the company’s commission fee was “completely unreasonable,” which is why he’s siding with Epic in the ongoing legal battle. 

Shortly after Musk’s initial tweet, Epic CEO Tim Sweeney took to Twitter to, once again, challenge Apple’s power.