Distinct() extension method problem with Object Initialisers

This code will fail:

var data = (from v in this.GetSession().Query<WorkCellLoadGraphData>()
where v.WorkCellId == "13"
select
new WorkCellLoadGraphData
{
RowId = v.RowId,
WorkCellId = v.WorkCellId,
WorkCellName = v.WorkCellName,
WorkCellGroupId = v.WorkCellGroupId,
WorkCellGroupName = v.WorkCellGroupName
});
return data.Distinct();

However, running this code:

var data = (from v in this.GetSession().Query<WorkCellLoadGraphData>()
where v.WorkCellId == "13"
select v
);
return data.Distinct();

will "work".

The error I get is: "Expression type 10005 is not supported by this SelectClauseVisitor."