Elon Musk waded into Apple Inc.’s legal battle over the fees it charges companies that use its app store, siding with “Fortnite” maker Epic Games Inc. in its antitrust case against the tech giant.

“Apple app store fees are a de facto global tax on the Internet,” the Tesla chief executive tweeted Friday. “Epic is right.”

Epic sued Apple last year, calling the company’s control over software developers monopolistic. In a federal trial that concluded in May, Epic CEO Tim Sweeneyaccused Apple of unfairly profiting from the work of videogame makers.

Apple has defended how it operates the app store and said Epic’s lawsuit was a basic disagreement over money. It takes as much as 30% of user spending that happens on most apps within its store. The company has said it spends money to ensure that the store provides a safe, secure way for users to download apps.

U.S. District Judge Yvonne Gonzalez Rogers is expected to make a ruling on the dispute in the coming months. She scrutinized Apple’s fees in the case and suggested the company doesn’t have enough competition and set the 30% commission arbitrarily. She also said she was concerned that Epic didn’t seem interested in paying Apple for access to customers.