in iOS10, Input.deviceOrientation always get the same value

I want to use Input .deviceOrientation to detect the phone orientation change and do some action as I need. So I use below code:

void Update() {
     if (Input.deviceOrientation == DeviceOrientation.LandscapeLeft) {
     else if (Input.deviceOrientation == DeviceOrientation.Portrait) {

This works well in Android devices, However, when run in ios10 ( I didn’t check other ios versions), the Input.deviceOrientation value is always the same no matter what orientation I lay my phone.

Could you please help me on that? why

Unity: 5.3.4f1 + ios10

More Info:

I use Debug.Log(Input.deviceOrientation) to get the orientation in logs, I am sure it always the same when I rotation my phone around the x, y, z axis.