Gentoo Nagios Emerge Checking Ping Syntax Freeze

Emerge was stuck during installing Nagios on Gentoo.

"
...
checking for ping... /bin/ping
checking for ping6... no
checking for ICMP ping syntax... /bin/ping -n -U -w %d -c %d %s
checking for ICMPv6 ping syntax... 
"

I think it is because of ping6 command missing.

[12:02:10] ccelebi@sandbox /bin $ ls -l /bin/ping*
-rws--x--x 1 root root 43280 May 11 04:21 /bin/ping
[12:02:20] ccelebi@sandbox /bin $ 

So I emerged nagios without ipv6 support. Hope it works.

EXTRA_ECONF="--with-ping-command=ping --with-ipv6=no" emerge nagios