ORDER SIBLINGS not working in Forms

I'm using Forms 9.0.4.0.19 (DS 10g).
Hierarchial query:

select level,empno, ename from emp
connect by prior
empno = mgr
start with mgr is null
order siblings by ename


is working fine in SQL prompt, and it's working in Forms Developer tree control,
List of values, Record groups ...


Problem is in PL/SQL Program Units and Trigger:

cursor some_tree  is select level,empno, ename from emp
connect by prior
empno = mgr
start with mgr is null
order siblings by ename

This will produce:

Error 103 at line x, column y
 Encountered the simbol "SIBLINGS" when expecting one of the following ...


Seems that Database PL/SQL engine supports clause ORDER SIBLINGS BY while Forms Builder does not.