RT-AC68U and miniupnpd problems

I'm constantly having problems with miniupnpd in RT-AC68U. After a day or two, the log is filled with these error messages:

May 17 15:48:48 miniupnpd[692]: accept(http): Too many open files
May 17 15:48:48 miniupnpd[692]: accept(http): Too many open files
May 17 15:48:48 miniupnpd[692]: accept(http): Too many open files
May 17 15:48:48 miniupnpd[692]: accept(http): Too many open files
May 17 15:48:48 miniupnpd[692]: accept(http): Too many open files
May 17 15:48:48 miniupnpd[692]:...

RT-AC68U and miniupnpd problems