NHibernate 1.2.1beta1

Named query :
that's a pretty simple query

<query name="EGroup_All">
from Domain.EGroup order by :SortExpression
</query>


at runtime, if i try to set namedparameter :SortExpression with something like "Description DESC", or (Domain.EGroup.Description ASC or something like an alias name) the resulting SQL generated from NHibernate loader as seen in logfiles does not have ORDER BY clause (that's it, the result set is unordered)

I'm maing something wrong? can i do that with another method?
thanx