ImmutablePath cannot be cast to org.apache.tinkerpop.gremlin.structure.Element

[hero78119]

Follow http://tinkerpop.apache.org/docs/3.2.1-SNAPSHOT/recipes/#shortest-path to try Shortest Test application on gremlin shell, but got the following stack trace.

java.lang.ClassCastException: org.apache.tinkerpop.gremlin.process.traversal.step.util.ImmutablePath cannot be cast to org.apache.tinkerpop.gremlin.structure.Element
        at com.thinkaurelius.titan.graphdb.tinkerpop.optimize.TitanPropertiesStep.flatMap(TitanPropertiesStep.java:109)
        at org.apache.tinkerpop.gremlin.process.traversal.step.map.FlatMapStep.processNextStart(FlatMapStep.java:47)
        at com.thinkaurelius.titan.graphdb.tinkerpop.optimize.TitanPropertiesStep.processNextStart(TitanPropertiesStep.java:93)
        at org.apache.tinkerpop.gremlin.process.traversal.step.util.AbstractStep.hasNext(AbstractStep.java:140)
        ...

Below is the simplified steps to reproduce errors on titan-1.0.0 version.

gremlin> v1 = graph.addVertex(T.label, 'v1')
gremlin> v2 = graph.addVertex(T.label, 'v2')
gremlin> v1.addEdge("foo", v2, "weight", 0.25f)
gremlin> g.V().hasLabel('v1').out().path().map(unfold().values('label'))
org.apache.tinkerpop.gremlin.process.traversal.step.util.ImmutablePath cannot be cast to org.apache.tinkerpop.gremlin.structure.Element
Display stack trace? [yN]