Impossible to load one-to-one association with LINQ for composite-id

When you use one-to-one mapping for object, that have with LINQ provider it's impossible to load property that contains associated object if it is not explicitly loaded in select clause.

Example:
<class name="ExternalField">
<composite-id>
<key-property name="Id" />
<key-property name="Id2" />
</composite-id>
</class>

<class name="Field">
<composite-id>
<key-property name="Id" />
<key-property name="Id2" />
</composite-id>
<one-to-one name="ExternalField" lazy="false" fetch="join" />
</class>
var fields = session.Query<Field>()
.ToList()
.Where(it => it.ExternalField != null).ToList();

There will be no object in final list, even if DB have such. Same queries work when using NHibernate.Linq.