SQL & PL/SQL :: Grouping Sets / Dictionary Views

I'm having a problem with grouping sets over dictionary views.

10g output:
SQL> select
2 -- 10g results
3 segment_name,
4 round(sum(bytes/1024/1024),2) mb
5 from dba_segments

[Code]...

ERROR at line 10: ORA-03001: unimplemented feature

Elapsed: 00:00:00.12

The query is fine over a non-dictionary table however (My actual code isnt against dual, but this makes it generic, the error is consistent)

11g output
SQL> select
2 -- 11g results
3 segment_name,
4 round(sum(bytes/1024/1024),2) mb
5 from dba_segments

[Code]....

ERROR at line 8: ORA-00904: : invalid identifier

Different error and that syntax, as far as I can tell, is sound - error message be damned.

An example of a query working on both versions is

select
employee_id,
sum(salary)
from
employees
group by grouping sets ((employee_id),null)
;

Am I missing something? Does grouping sets not work over the dictionary views?

Edit: Added version tags over the code to make it easier to read