Kinect prevents sleep on OS X

This is not strictly a OF app question.

I work on OS X 10.10 - 10.11
The mac mini does not really go to sleep while a kinect-for_windows is connected, without an OF app running.
The display goes to sleep, for a short moment the mac mini led pulses and indicates a proper sleep. But after a while the led gets solid and the computer wakes up, but the display is still asleep.
I used a simple log app to see that computer was not sleeping.

So, kinect allows mac mini to do display sleep but not proper sleep.

Without kinect connected sleep behaviour is as expected.
Also, with kinect 360 sleep behaviour is as expected.

Did anyone else see this and may have found a solution?

Thanks.