Undefined ${appserver.home} and ${appserver.base}

When I run:
mvn jetty:run
from trunk at r538691, the "appserver.base" property is undefined, resulting in the creation of this directory:
Directory of C:\dev\apache-maven\archiva\archiva-web\archiva-webapp
05/17/2007 02:24 PM <DIR> ${appserver.base}
05/16/2007 11:40 AM 14,681 pom.xml
05/16/2007 11:40 AM <DIR> src
05/17/2007 11:06 AM <DIR> target