[exim] control condition in acl_smtp_connect

I'm trying to turn on enforce_sync for a single host. The examples I've
been able to find for this suggest doing it in the acl_smtp_connect,
however I can't seem to get it to work. Please help.

I have the following:

acl_smtp_connect = smtp_connect

smtp_connect:
  accept hosts = +no_sync_hosts
         control = no_enforce_sync
  accept

But, exim doesn't like this:

Oct 3 21:09:29 insomnia exim[28581]: H=xx [xx.xx.xx.xx] temporarily
rejected connection in "connect" ACL: cannot use control condition in
connection ACL

This is with Exim 4.42.