7.1current: order by func in union

> PostgreSQL 7.0.3 on sparc-sun-solaris2.6, compiled by gcc 2.95.2
...
> test=# select x from tryam union select x from tryam order by 
> length(x);
>  x  
> ----
>  1
>  22
>  1
>  22
> (4 rows)

7.1current:

vac=# select x from tryam union select x from tryam order by length(x);
ERROR:  Attribute 'x' not found

Vadim