Executable model compilation fails with java.lang.RuntimeException: Unknown expression type: -1

eval( functions.add($age, -1).compareTo(10) < 0)

java.lang.RuntimeException: Unknown expression type: -1
	at org.drools.modelcompiler.builder.generator.DrlxParseUtil.getExpressionType(DrlxParseUtil.java:245)
	at org.drools.modelcompiler.builder.generator.expressiontyper.ExpressionTyper.processFirstNode(ExpressionTyper.java:562)
	at org.drools.modelcompiler.builder.generator.expressiontyper.ExpressionTyper.toTypedExpressionFromMethodCallOrField(ExpressionTyper.java:380)
	at org.drools.modelcompiler.builder.generator.expressiontyper.ExpressionTyper.parseNodeArguments(ExpressionTyper.java:679)
	at org.drools.modelcompiler.builder.generator.expressiontyper.ExpressionTyper.parseMethodCallExpr(ExpressionTyper.java:647)
	at org.drools.modelcompiler.builder.generator.expressiontyper.ExpressionTyper.methodCallExpr(ExpressionTyper.java:635)
	at org.drools.modelcompiler.builder.generator.expressiontyper.ExpressionTyper.toTypedExpressionFromMethodCallOrField(ExpressionTyper.java:416)
	at org.drools.modelcompiler.builder.generator.expressiontyper.ExpressionTyper.toTypedExpressionRec(ExpressionTyper.java:191)
	at org.drools.modelcompiler.builder.generator.expressiontyper.ExpressionTyper.toTypedExpression(ExpressionTyper.java:121)
	at org.drools.modelcompiler.builder.generator.drlxparse.ConstraintParser.parseBinaryExpr(ConstraintParser.java:269)
	at org.drools.modelcompiler.builder.generator.drlxparse.ConstraintParser.getDrlxParseResult(ConstraintParser.java:89)
	at org.drools.modelcompiler.builder.generator.drlxparse.ConstraintParser.drlxParse(ConstraintParser.java:56)
	at org.drools.modelcompiler.builder.generator.drlxparse.ConstraintParser.drlxParse(ConstraintParser.java:51)
	at org.drools.modelcompiler.builder.generator.drlxparse.ConstraintParser.drlxParse(ConstraintParser.java:47)
	at org.drools.modelcompiler.builder.generator.visitor.EvalVisitor.visit(EvalVisitor.java:25)
	at org.drools.modelcompiler.builder.generator.visitor.ModelGeneratorVisitor.visit(ModelGeneratorVisitor.java:94)
	at org.drools.compiler.lang.descr.EvalDescr.accept(EvalDescr.java:97)
	at org.drools.modelcompiler.builder.generator.visitor.AndVisitor.visit(AndVisitor.java:29)
	at org.drools.modelcompiler.builder.generator.visitor.ModelGeneratorVisitor.visit(ModelGeneratorVisitor.java:69)
	at org.drools.modelcompiler.builder.generator.ModelGenerator.processRule(ModelGenerator.java:173)
	at org.drools.modelcompiler.builder.generator.ModelGenerator.generateModel(ModelGenerator.java:153)
	at org.drools.modelcompiler.builder.ModelBuilderImpl.compileKnowledgePackages(ModelBuilderImpl.java:169)
	at org.drools.modelcompiler.builder.ModelBuilderImpl.buildRules(ModelBuilderImpl.java:119)
	at org.drools.modelcompiler.builder.ModelBuilderImpl.buildPackages(ModelBuilderImpl.java:69)
	at org.drools.compiler.builder.impl.CompositeKnowledgeBuilderImpl.build(CompositeKnowledgeBuilderImpl.java:108)
	at org.drools.compiler.builder.impl.CompositeKnowledgeBuilderImpl.build(CompositeKnowledgeBuilderImpl.java:100)
	at org.drools.compiler.kie.builder.impl.AbstractKieProject.buildKnowledgePackages(AbstractKieProject.java:261)
	at org.drools.compiler.kie.builder.impl.AbstractKieProject.verify(AbstractKieProject.java:75)
	at org.drools.compiler.kie.builder.impl.KieBuilderImpl.buildKieProject(KieBuilderImpl.java:271)
	at org.drools.compiler.kie.builder.impl.KieBuilderImpl.buildAll(KieBuilderImpl.java:239)
	at org.drools.compiler.kie.builder.impl.KieBuilderImpl.buildAll(KieBuilderImpl.java:208)
	at org.drools.compiler.kie.builder.impl.KieBuilderImpl.buildAll(KieBuilderImpl.java:196)
	at org.drools.modelcompiler.BaseModelTest.createKieBuilder(BaseModelTest.java:144)
	at org.drools.modelcompiler.BaseModelTest.createKieBuilder(BaseModelTest.java:125)
	at org.drools.modelcompiler.BaseModelTest.getKieContainer(BaseModelTest.java:114)
	at org.drools.modelcompiler.BaseModelTest.getKieContainer(BaseModelTest.java:107)
	at org.drools.modelcompiler.BaseModelTest.getKieSession(BaseModelTest.java:103)
	at org.drools.modelcompiler.BaseModelTest.getKieSession(BaseModelTest.java:99)
	at org.drools.modelcompiler.CompilerTest.testEvalExprWithFunctionCall(CompilerTest.java:1997)