Oracle OLAP Java Api Source.recursiveJoin filters null measures

I'm using the OLAP (11gR2) Java Api to query the AW.
I'm trying to sort a measure based on a hierarchy. This measure has null values in it.

I'm using the following code snippet to query the AW
       ...

/* 1*/ Source row=rowHier.getSource();
/* 2*/ row=row.join(row.value(), new String[]{"SALES_TERRITORY::ALL_CUSTOMERS::1", "SALES_TERRITORY::AREA::Area 1", "SALES_TERRITORY::AREA::Area 2", "SALES_TERRITORY::AREA::Area 3"});
/* 3*/ Source column=colHier.getSource();
/* 4*/ column=column.join(column.value(), "CALENDAR::DAY::30-JUN-11");
/* 5*/ Source page=pagHier.getSource();
/* 6*/ page=page.join(page.value(), "PRODUCT_CLASS_HIER::ALL_PRODUCTS::1");
/* 7*/ Source source=measure.getSource();
/* 8*/ row=row.recursiveJoin(source, source.getDataType(), rowHier.getParentAttribute().getSource(), Source.COMPARISON_RULE_DESCENDING_NULLS_FIRST);