NullPointerException @SchemaTypeImpl.setShortJavaName(SchemaTypeImpl.java:532)

I get the following NullPointerException when attempting to compile the
synthesys.xsd found at http://www.w3.org/TR/speech-synthesis/synthesis.xsd

Exception in thread "main" java.lang.NullPointerException
at
org.apache.xmlbeans.impl.schema.SchemaTypeImpl.setShortJavaName(SchemaTypeImpl.java:532)
at
org.apache.xmlbeans.impl.schema.StscJavaizer.assignJavaAnonymousTypeNames(StscJavaizer.java:326)
at org.apache.xmlbeans.impl.schema.StscJavaizer.javaizeType(StscJavaizer.java:259)
at org.apache.xmlbeans.impl.schema.StscJavaizer.javaizeType(StscJavaizer.java:214)
at
org.apache.xmlbeans.impl.schema.StscJavaizer.javaizeAllTypes(StscJavaizer.java:100)
at
org.apache.xmlbeans.impl.schema.SchemaTypeSystemCompiler.compileImpl(SchemaTypeSystemCompiler.java:244)
at
org.apache.xmlbeans.impl.schema.SchemaTypeSystemCompiler.compile(SchemaTypeSystemCompiler.java:185)
at
org.apache.xmlbeans.impl.tool.SchemaCompiler.loadTypeSystem(SchemaCompiler.java:771)
at org.apache.xmlbeans.impl.tool.SchemaCompiler.compile(SchemaCompiler.java:823)
at org.apache.xmlbeans.impl.tool.SchemaCompiler.main(SchemaCompiler.java:305)
at com.globalsymmetry.xmlbeans.Main.main(Main.java:13)