[wmii] wmiir "cannot write file" error

Eager to try out the irssi notifier script that was recently posted, I
noticed the "Urgent" /ctl/ command which I haven't seen before. I
decided to try it out to see what exactly it does. However, when I try
to use it on any of my windows I get:

caleb_AT_pintsize:~$ wmiir xwrite /client/0x140000a/ctl Urgent
wmiir: fatal: cannot write file '/client/0x140000a/ctl': bad usage

I'm using wmii-3.6, just downloaded it a couple of days ago from
Ubuntu's repos. I've tried NotUrgent, Fullscreen and NotFullscreen
with the same results (kill works). I see on the man page that I
_should_ be able to do this. Any idea what I'm doing wrong? Thanks.

-- 
Caleb Eggensperger
http://calebegg.com/