Property Path support in Fuseki

[Eric Scott]

I'm having trouble getting property paths to work under fuseki. Here's a 
minimal pair:

This query works fine (I've denatured some of the names):
        SELECT ?myClass  ?childClass
        WHERE
        {
            BIND (<MyURL> as ?myClass)
            ?childClass rdfs:subClassOf ?myClass.

        }
It gives me all the immediate subclasses of <MyURL>.

But this does not:
        SELECT ?myClass  ?descendentClass
        WHERE
        {
            BIND (<MyURL> as ?myClass)
            ?descendentClass rdfs:subClassOf+ ?myClass.

        }

Which I would expect to give me all the descendent classes of <MyURL>

The error is:
Execption type: java.lang.Exception
Exception in thread "main" java.lang.Exception: FUSEKI ERROR:
Error 500: OpPath


Is there some assembler declaration I need in my fuseki configuration to 
enable property paths?

Thanks,