Oracle Database Discussions

It's strange, but it seems that Oracle ODBC doesn't support requests to stored procedures with UNION function.
I'm using following construction in stored proc:

open a for select * from
(
with rez1 as ( select ....... ),
rez2 as ( select ....... )
select * from rez1
union
select * from rez2
)

and when I call it from Excel I receive ORA-32036 (unsupported case for inlining of query name in WITH clause).
But if I start that proc from SQL Navigator then everything is fine, proc returns results (REF CURSOR)

And if I remove that UNION (together with "select * from rez2), request also works fine from Excel...

Is there some error in my proc or it's just a limitation of ODBC?