OOPath use with primitives does not return any match

    @Test
    public void testPrimitives() {
        String drl =
                "import org.drools.compiler.xpath.*;\n" +
                "global java.util.List list\n" +
                "\n" +
                "rule R when\n" +
                "  Adult( $x: /children.age )\n" +
                "then\n" +
                "  list.add( $x );\n" +
                "end\n";
        
        System.out.println(drl);

        KieSession ksession = new KieHelper().addContent( drl, ResourceType.DRL )
                                             .build()
                                             .newKieSession();

        List<String> list = new ArrayList<String>();
        ksession.setGlobal( "list", list );

        Man bob = new Man( "Bob", 40 );
        bob.addChild( new Child( "Charles", 12 ) );
        bob.addChild( new Child( "Debbie", 8 ) );

        ksession.insert( bob );
        ksession.fireAllRules();
        
        assertEquals(2, list.size());

    }

rule R when
  Adult( $x: /children.name )
then
  ...