Perforce problem: incorrect client spec is used

I have 2 projects set up which use the same perforce scm url. One is run each 5 mins, the other is a nightly tests build. I've noticed that the latter never gets run-the message is that the dir is up-to date. It appeared that after the first project is run, its client spec is set to system variable in PerforceCheckOutCommand (maven-scm perforce provider) class and afterwards the value of the var is used instead of a correct client spec. I didn't remove the property set, as it is a fix to SCM-165, but rather the place where prop is used. Now works fine.
Patch is attached.