Group by x,x,x with rollup works, group by rollup (x,x,x) doesn't 2005

I'm trying to use the rollup function. The sql server 2005 manual states that 'with rollup' is not ISO standard, and will be removed, don't do any development work with this format, by which I presume they mean use the 'group by rollup' function. They give the example code below in the documentation

SELECT a, b, c, SUM ( <expression> )
FROM T
GROUP BY ROLLUP (a,b,c);

Select allOpen in new window

I have tried this and it returns

Msg 195, Level 15, State 10, Line 3
'ROLLUP' is not a recognized built-in function name.

The database is set to level 90 (SQL 2005)

I am probably going to go with using 'with rollup' for now, but just want to check that the SQL documentation is actually wrong for this function. Or do I need to check for patches to the SQL server engine?