NHibernate LINQ - SQL command strings interning

Question

I just ran a memory profiler on a .NET app and noticed that there were many sets of duplicated strings in the finalizer queue, all generated by same NHibernate LINQ queries.

I thought these strings were supposed to be cached/interned? I find it weird that NH Linq doesn't do some expression -> generated string caching; it seems very unlikely that each expression is compiled to SQL on each call? Is this a setting of some kind, or am I doing something wrong?

Queries are quite simple, i.e. most of them don't even have parameters:

 var results = session
      .Query<Request>()
      .Where(req => !req.IsCanceled);

I am using the NHibernate.Driver.SqlClientDriver with NHibernate.Dialect.MsSql2008Dialect.