Catch onKeyLongPress() using Android6 does not work any more

I’m developing a TV application on Shield using the remote controll.
The application used the key long-press feature for the back button. It worked all fine until I upgraded to Android6 last week.

The overrided Activity.onKeyLongPress(int keyCode, KeyEvent event)callback is not triggered any more
(worked fine before the upgrade; the RC got its upgrade as well ans has v0.82 loaded).

A short click on the back button triggers the onKeyDown and the onKeyUp event as it is expected.
Connected over ADB I see the underlaying NVHandler logging out first “Injecting long-press request” then “Injecting single-tap request”.
A long click on the back button does NOT trigger any onKey* event, even not a onKeyDown or onKeyUp. And the debug logging shows the NVHandler reports only the “Injecting long-press request”, but nothing that would follow.

Is the gone “KeyLongPress” a bug or is it on purpose?