Svk tells "XXX is not a mirrored path" when I use no XXX

I got the error, xxx is not a mirrored path", from svk, when I try to create other new mirror depot. Although xxx is one of svk work depot, I did not use the xxx at that time.

• #>svk mirror //mirror/zzz svn://yyy/xvn/zzz
• XXX is not a mirrored path.

I googled such problem and its solutions. Then, I found that I have committed the xxx into not work depot but mirror depot of svk by mistake. It may cause the error on xxx.
To recover it, I tried to detach the xxx from the mirror once, but the detachment failed, too. Furthermore, svk has --recover option but it is not supported yet. I gave up recovery and rebuilt svk depot again...
Svk's source code written in Perl contains this error message at several places, which I do not recommend because I was hard to find out the code that caused the error. I think that error messages for engineer should be unique.