Can't configure the ResourceCollection with maven

I tried following the instructions <a href="http://docs.codehaus.org/display/JETTY/Multiple+WebApp+Source+Directory">Multiple WebApp Source Directory</a>, but maven is giving an error when trying to configure the ResourceCollection. It looks like maven is having problems with the overloaded setters. It is is trying to use ResourceCollection.setResources(Resource[]) instead of ResourceColection.setResources(String).

$mvn jetty:run
...
[ERROR] BUILD ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Failed to configure plugin parameters for: org.mortbay.jetty:maven-jetty-plugin:6.1.12rc1

(found static expression: 'src/main/webapp,target/mlsdb' which may act as a default value).

Cause: Cannot assign configuration entry 'resources' to 'class [Lorg.mortbay.resource.Resource;' from 'src/main/webapp,target/mlsdb', which is of type class java.lang.String

pom.xml:
...
<plugin>
<groupId>org.mortbay.jetty</groupId>
<artifactId>maven-jetty-plugin</artifactId>
<configuration>
<webAppConfig>
<contextPath>/</contextPath>
<baseResource implementation="org.mortbay.resource.ResourceCollection">
<resources>src/main/webapp,target/mlsdb</resources>
</baseResource>
</webAppConfig>
</configuration>
</plugin>

$ mvn -v
Using Java version: 1.6
Maven version: 2.0.9
Java version: 1.6.0_05
OS name: "mac os x" version: "10.5.4" arch: "x86_64" Family: "mac"