ClassCastException / crash when running --make-species-subset

Hi.

We're having trouble with processing the latest go-plus.owl with owltools.

With this command line:

(cd /tmp/; wget http://purl.obolibrary.org/obo/go/extensions/go-plus.owl) &&
(cd go-svn/ontology/extensions; owltools /tmp/go-plus.owl --use-catalog --reasoner elk --make-species-subset -t NCBITaxon:4896 -o -f obo /tmp/go-plus-pombe-only.obo)

we get this exception:

2018-08-06 21:53:38,189 WARN  (IndexedObjectUnionOf:92) [reasoner.indexing.IndexedObjectUnionOf]ELK does not support positive occurrences of ObjectUnionOf. Reasoning might be incomplete!
2018-08-06 21:53:38,190 WARN  (ChangeIndexingProcessor:66) [reasoner.indexing.axiomIgnored]ELK does not support ObjectMinCardinality. Axiom ignored:
EquivalentClasses(<http://purl.obolibrary.org/obo/UBERON_0000037> ObjectIntersectionOf(<http://purl.obolibrary.org/obo/UBERON_0001305> ObjectSomeValuesFrom(<http://purl.obolibrary.org/obo/BFO_0000051> <http://purl.obolibrary.org/obo/UBERON_0000039>) ObjectMinCardinality(2 <http://purl.obolibrary.org/obo/RO_0002180>)))
2018-08-06 21:53:38,192 WARN  (ChangeIndexingProcessor:66) [reasoner.indexing.axiomIgnored]ELK does not support InverseObjectProperties. Axiom ignored:
InverseObjectProperties(<http://purl.obolibrary.org/obo/RO_0002005> <http://purl.obolibrary.org/obo/RO_0002134>)
Exception in thread "main" java.lang.ClassCastException: uk.ac.manchester.cs.owl.owlapi.OWLLiteralImplString cannot be cast to org.semanticweb.owlapi.model.IRI
        at org.obolibrary.macro.MacroExpansionVisitor$MacroExpansions.expand(MacroExpansionVisitor.java:162)
        at org.obolibrary.macro.MacroExpansionVisitor$MacroExpansions.<init>(MacroExpansionVisitor.java:122)
        at org.obolibrary.macro.MacroExpansionVisitor.expandAll(MacroExpansionVisitor.java:95)
        at owltools.mooncat.SpeciesSubsetterUtil.<init>(SpeciesSubsetterUtil.java:139)
        at owltools.cli.CommandRunner.runSingleIteration(CommandRunner.java:768)
        at owltools.cli.CommandRunnerBase.run(CommandRunnerBase.java:76)
        at owltools.cli.CommandRunnerBase.run(CommandRunnerBase.java:68)
        at owltools.cli.CommandLineInterface.main(CommandLineInterface.java:12)

It last worked successfully on August 2nd.

Thanks in advance.

CC: @ValWood

Reproduce the reported command using the downloaded go-plus.owl, then inspect MacroExpansionVisitor.java at line 162 and SpeciesSubsetterUtil.java at line 139, where the stack trace enters the failing path. Done means --make-species-subset completes without the ClassCastException and produces the requested OBO output.