ClassCasException when upgrading from 0.2.1 to 0.3.1

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Exception in thread "main" java.lang.ClassCastException: com.thinkaurelius.titan.graphdb.types.system.SystemKey cannot be cast to com.thinkaurelius.titan.graphdb.internal.AbstractElement
	at com.thinkaurelius.titan.graphdb.internal.AbstractElement.equals(AbstractElement.java:40)
	at com.thinkaurelius.titan.graphdb.transaction.indexcache.SimpleIndexCache$1.apply(SimpleIndexCache.java:38)
	at com.thinkaurelius.titan.graphdb.transaction.indexcache.SimpleIndexCache$1.apply(SimpleIndexCache.java:35)
	at com.google.common.collect.Iterators$8.computeNext(Iterators.java:736)
	at com.google.common.collect.AbstractIterator.tryToComputeNext(AbstractIterator.java:143)
	at com.google.common.collect.AbstractIterator.hasNext(AbstractIterator.java:138)
	at com.google.common.collect.TransformedIterator.hasNext(TransformedIterator.java:43)
	at com.google.common.collect.Iterators$8.computeNext(Iterators.java:734)
	at com.google.common.collect.AbstractIterator.tryToComputeNext(AbstractIterator.java:143)
	at com.google.common.collect.AbstractIterator.hasNext(AbstractIterator.java:138)
	at com.google.common.collect.Sets.newHashSet(Sets.java:250)
	at com.thinkaurelius.titan.graphdb.query.QueryProcessor.getUnwrappedIterator(QueryProcessor.java:69)
	at com.thinkaurelius.titan.graphdb.query.QueryProcessor$OuterIterator.<init>(QueryProcessor.java:132)
	at com.thinkaurelius.titan.graphdb.query.QueryProcessor.iterator(QueryProcessor.java:48)
	at com.google.common.collect.Iterables$7.iterator(Iterables.java:611)
	at com.google.common.collect.Iterables.getOnlyElement(Iterables.java:282)
	at com.thinkaurelius.titan.graphdb.transaction.StandardTitanTx.getType(StandardTitanTx.java:488)
	at com.thinkaurelius.titan.graphdb.transaction.StandardTitanTx.getEdgeLabel(StandardTitanTx.java:517)
	at com.thinkaurelius.titan.graphdb.blueprints.TitanBlueprintsTransaction.addEdge(TitanBlueprintsTransaction.java:101)
	at com.thinkaurelius.titan.graphdb.blueprints.TitanBlueprintsTransaction.addEdge(TitanBlueprintsTransaction.java:96)
	at com.thinkaurelius.titan.graphdb.blueprints.TitanBlueprintsGraph.addEdge(TitanBlueprintsGraph.java:173)
	at com.tinkerpop.blueprints.util.wrappers.batch.BatchGraph.addEdge(BatchGraph.java:359)
	at com.tinkerpop.blueprints.util.io.graphson.GraphElementFactory.createEdge(GraphElementFactory.java:23)
	at com.tinkerpop.blueprints.util.io.graphson.GraphSONUtility.edgeFromJson(GraphSONUtility.java:173)
	at com.tinkerpop.blueprints.util.io.graphson.GraphSONReader.inputGraph(GraphSONReader.java:166)
	at com.tinkerpop.blueprints.util.io.graphson.GraphSONReader.inputGraph(GraphSONReader.java:104)
	at com.tinkerpop.blueprints.util.io.graphson.GraphSONReader.inputGraph(GraphSONReader.java:88)