Surface - No Low Battery Notification?

When I first got my Surface, I used to get a low battery notification when the device got to 6%, and then a warning that it was about to shut down when it got to 3%. It works similar on my Windows 8 PC.

However, now that notification never happens. The device just shuts down out of the blue. I've checked the Power Options, and they haven't changed. I don't know if it's an update causing this, or just something on my system, but has anyone else noticed this?