Apple is being accused of ripping off a very popular app that would allow jailbroken iOS users to change the lighting on their devices.

Some are accusing the tech giant of essentially copying F.lux, which was then redubbed Night Shift for the iOS 9.3. The app would limit the blue light of the phone to keep it from interrupting people’s sleep, according to a Forbes report.

And this comes after Apple reportedly contacted F.lux in November to ask them to cease and desist, perhaps to reduce competition with Night Shift — so there’s no question Apple knew it existed beforehand.

F.lux created their app to reduce the amount of blue spectrum light emitted by your Apple device, which would reduce its impact on sleep quality.

Just like F.lux, Apple’s Night Shift allows users to set Kelvin-scale light levels at certain times. It’s essentially the same app, critics argue, and it doesn’t make Apple look very good.

F.lux’s app has been around since 2012, and the team became angered when four years later Apple attempts to block them entirely while releasing a feature that does the exact same thing, all the while acting as if Night Shift was Apple’s idea, according to the report.

In a statement, F.lux hit back at Apple’s move:

“We’re proud that we are the original innovators and leaders in this area. In our continued work over the last seven years, we have learned how complicated people actually are. The next phase of f.lux is something we cannot wait to ship to the world,” the statement reads. “Today we call on Apple to allow us to release f.lux on iOS, to open up access to the features announced this week, and to support our goal of furthering research in sleep and chronobiology.”