Can't locate package Irssi::Nick for @Irssi::Irc::Nick::ISA

[pc-coholic]

Since upgrading to version 18 of IrssiNotifier, I get this error from time to time:

Can't locate package Irssi::Nick for @Irssi::Irc::Nick::ISA at /home/mgr/.irssi/scripts/autorun/irssinotifier.pl line 439.

The same problem has also been described here: http://bugs.irssi.org/index.php?do=details&task_id=242

The suggested solution there is to add

{ package Irssi::Nick }

to the script.

I'm posting this issue here, but at this precise moment, I fail to reproduce the bug - so I can't verify the solution at the moment either...