Apple's iOS 9 reportedly has a bug that may make it impossible for iPhone owners to use certain apps on a cellular network.

As with previous versions of iOS, iOS 9 lets you stop your phone from using cellular data with certain apps (Settings > Cellular > Use Cellular Data For). The issue, however, is that iOS 9 doesn't allow apps to use cellular data once they've been toggled off, according to a new report from Wayne Williams at Beta News.

Williams reported on Monday that he was unable to use certain apps while on a cellular network. He went into settings and toggled those apps to "on" so they could tap into cellular data. But as soon as he left the Settings menu, his settings reverted back to "off," meaning they were useless unless he was on a Wi-Fi network.

The issue appears to affect devices upgraded from iOS 8 to iOS 9. According to Williams—and many iOS 9 users who have taken to Apple's Support forums to complain of the problem—if an app in iOS 8 was allowed to access cellular data, it works in iOS 9. If it was set to not access that data in iOS 8, however, it refuses to access cellular data in iOS 9, even if you grant permission.

Williams upgraded his iPhone 5s from iOS 8 to iOS 9. He then purchased a new iPhone 6s and installed from a backup, which happened to be the version of iOS 9 on his 5s that included the cellular network bug.

Williams said he has two options: restore his phone from a pre-iOS 9 backup (which he doesn't have); or set up his iPhone as a new iPhone, which will require him to install all his apps one by one.

"Both choices are highly unsatisfactory," he wrote. "It might be addressed in iOS 9.0.2, but there's no guarantee that will be the case."

Apple's iOS 9 launched about two weeks ago and is already running on 50 percent of iOS devices. With the arrival of the the iPhone 6s and 6s Plus on Friday, sales of which have topped 13 million, that number is likely much higher now.

It's not uncommon for new operating systems to suffer from bugs. Indeed, iOS 8 was hit with several issues when it launched last year, from slow Wi-Fi to battery drains.

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