[Fail2ban-users] WARNING Unable to find a corresponding IP address for ::1

[<per...@dp...>]

Hi,
I'm using fail2ban with SSLH multiplexer.

SSLH runs in transparent mode so the real ip address is logged in logs.

Every time that there is an attemp against my server fail2ban says this 
on my console:
fail2ban.filter : WARNING Unable to find a corresponding IP address for ::1

what does it means?
How to remove that warning?

Thanks