SSL and systemd

I have panda-imap running on CentOS 7 with xinetd.
We wanted to implement it using a systemd service instead, so I made 
files
/usr/lib/systemd/system/[email protected] imaps.socket imap.socket 
[email protected]

The server appears to work on port 143 with STARTTLS (or notls)

But on port 993 it responds with plaintext.

If I enable DEBUG logging in syslog, with xinetd I get messages like
  Login user=andrew host=blah.example.com [192.168.2.3]
  imaps SSL service init from 192.168.2.3
but with systemd service I get
  Login user=andrew host=[NON-IPv4]
  Line too long before authentication host=[NON-IPv4]

I suspect some code in server_init in osdep/unix/env_unix.c
which I don't entirely understand


Has anyone solved this ?