HudsonでのGriffonプロジェクトのビルドがうまくいかない

cd $WORKSPACE/griffon-test
$GRIFFON_HOME/bin/griffon package

+ /usr/share/griffon/bin/griffon package
    Welcome to Griffon 0.2 - http://griffon.codehaus.org/
    Licensed under Apache Standard License 2.0
    Griffon home is set to: /usr/share/griffon
    Base Directory: /var/lib/hudson/jobs/griffon-test/workspace/griffon-test
    Running script /usr/share/griffon/scripts/Package.groovy
    Environment set to production
    Found events script in plugin css-builder-0.2
    groovy.lang.MissingMethodException: No signature of method: groovy.util.ConfigObject.minus() is applicable for argument types: (null) values: [null]
    at Application$_run_closure2.doCall(Application.groovy:7)
    at Application$_run_closure2.doCall(Application.groovy)
    at Application.run(Application.groovy:6)
    at _GriffonPackage_groovy$_run_closure1.doCall(_GriffonPackage_groovy:72)
    at _GriffonPackage_groovy$_run_closure1.doCall(_GriffonPackage_groovy)
    at Package$_run_closure2.doCall(Package:55)
    at Package$_run_closure2.doCall(Package)
    at Package$_run_closure3.doCall(Package:71)
    at Package$_run_closure3.doCall(Package)
    at Package$_run_closure1.doCall(Package:33)
    at Package$_run_closure1.doCall(Package)
    at gant.Gant$_dispatch_closure4.doCall(Gant.groovy:306)
    at gant.Gant.dispatch(Gant.groovy:316)
    at gant.Gant.this$2$dispatch(Gant.groovy)
    at gant.Gant.invokeMethod(Gant.groovy)
    at gant.Gant.processTargets(Gant.groovy:446)
    at gant.Gant.processTargets(Gant.groovy:430)
    Failed to compile Application configuration file: No signature of method: groovy.util.ConfigObject.minus() is applicable for argument types: (null) values: [null]