as per the following email thread in jbpm-dev: http://lists.jboss.org/pipermail/jbpm-dev/2013-August/004100.html
fix for this has been committed into master and 6.0.x https://github.com/droolsjbpm/jbpm/commit/0502badfa4371ba5d4ed8222d15fe627ae734aaf
Verified in BPMS 6 ER4 (redhat-4).