Screen.sleepTimout also affects the iOS while app is in background (ipad)

On an iPad, we set the Screen.sleepTimeout to NeverSleep and it works but it also works when the game is running in the background. As you can't really exit applications on iOS, this changes the user's experience on the iPad, preventing it from ever going to sleep. We tried changing this value back on onApplicationPause but it doesn't register... Any suggestions? (Or maybe it's a Unity bug?)