Since its launch in 2015, Apple has increasingly positioned the Apple Watch as a health and fitness device; something that helps users track their workouts and look after their body. But one popular feature has been missing from Apple’s built-in software: sleep-tracking.

Not for much longer, says Bloomberg. The publication reports that Apple is testing sleep tracking functionality and, if it meets standards, plans to add it to the Apple Watch by 2020.

You can already track your sleep on the Apple Watch using third-party apps, but the device has always been hamstrung in this regard by its relatively slim battery life. Apple promises users a full day’s use from the watch before charging it overnight (and this often looks more like two days’ use, depending on usage), but that’s not enough for regular sleep tracking. Rival fitness-focused wearables with sleep tracking like the Fitbit Versa or Withings Steel Hybrid Smartwatch, for example, last up to weeks before needing a charge.

Bloomberg’s Mark Gurman notes that in order to make sleep-tracking functional for the Apple Watch, the company will need to increase its battery life or find a way to run sleep tracking in a low-power mode overnight. Or, if charging speeds increase, it could just ask users to top up their batteries in the morning.

With sleep tracking built into the Apple Watch the company would increase its range of health tracking features, which now take in everything from electrocardiograms (added in the Apple Watch Series 4) to automatic workout detection (added in watchOS 5). Adding sleep tracking to this bundle would be another reason not to take the Apple Watch off your wrist.