Not compatible with 4.0?

Why does this page says compatible with upto Nagios 3.0?

NRPE used to work with Nagios 3.0 in our environment. But ever since we upgraded to Nagios core 4.0.7 NRPE started giving error:
Aug 13 08:55:25 web1 xinetd[6076]: START: nrpe pid=4422 from=::ffff:210.21.7.1
Aug 13 08:55:25 web1 xinetd[4422]: FAIL: nrpe address from=::ffff:210.21.7.1
Aug 13 08:55:25 web1 xinetd[6076]: EXIT: nrpe status=0 pid=4422 duration=0(sec)
Note: IP is allowed in xinetd config.