Real Time Visitor Count no longer shows idle visitors

After updating Piwik to version 2.16.2, Real Time Visitor Count does not count visitors, wich are on an active window but idle (reading contents of the page).

The heartbeat Timer is activated, in apache accesslog heartbeat accesses are logged:

"GET /piwik.php?ping=1&idsite=1…


Maybe this behavior changed. Do you mind creating a report on our tracker: Issues · piwik/piwik · GitHub