When you buy a game console, smartphone, dryer, vacuum cleaner, or any number of other complicated electronics, there’s usually a sticker or a piece of paperwork telling you that trying to repair the device yourself will void your warranty. That’s illegal under the federal Magnuson-Moss Warranty Act. Companies offering a warranty on their goods aren’t allowed to void that warranty if the user attempts to repair it themself, but that doesn’t stop the company from scaring customers into thinking it’s true.

It’s such a huge problem that US PIRG—a non-profit that uses grassroots methods to advocate for political change—found that 90 percent of manufacturers it contacted claimed that a third party repair would void its warranty. PIRG researched the warranty information of 50 companies in the Association of Home Appliance Manufacturers (AHAM)—an industry group of notorious for lobbying to protect is repair monopolies—and found that 45 of them claimed independent repair would void their warranty.

PIRG poured over the documentation for 50 companies such as Bissell, Whirlpool, and Panasonic to document their warranty policies. When it couldn’t find clear language about warranty and repair, it reached out to the companies via their customer service lines. The overwhelming majority of the companies told PIRG that independent repair would void the warranty.

“Warranties should honor our right to repair,” Nathan Proctor, Director of the Campaign for the Right to Repair at US PIRG, told Motherboard via email. “By casting independent repair as dangerous, the companies reinforce the idea that only they can fix these products. Not only is that untrue, it adds to the growing problem of disposable electronics and appliances.”

The 1975 Magnuson-Moss Warranty Act states that no manufacturer who charges more than $5 for a product can put repair restrictions on a product they’re offering a warranty on. In May, the US Federal Trade Commission sent warning letters to Sony, Microsoft, Nintendo, HTC, Hyundai, and ASUS for violating the act by threatening to void the warranties of customers who repaired their own devices. Within 30 days, many of the companies had complied and changed the language on their websites around indepent repair.