(auto) De-referencing not working as expected using select_related

I have two models that are related. User, and Role

class Role(Document):
    name = StringField(required=True)
    project = ReferenceField(Project, reverse_delete_rule=CASCADE)
    description = StringField(required=True)
    permissions = ListField(EmbeddedDocumentField(Permission))

class User(Document):
    full_name = StringField(required=True)
    username = EmailField(required=True)
    password_hash = StringField(required=True)
    avatar = StringField()
    date_created = DateTimeField(default=datetime.datetime.utcnow)
    project = ReferenceField(Project, reverse_delete_rule=CASCADE)
    role = ReferenceField(Role, reverse_delete_rule=DENY)

I can't seem to figure out how to obtain a User document that has the role and project fields dereferenced. My initial solution was to call select_related() on the QuerySet containing a selection of users.

users = User.objects(project=project_id).select_related()

This has no effect. type(users[0].role) == ReferenceField, and not Role. I read in the documentation that ReferenceFields should be dereferenced automatically by default (because _auto_dereference is set to True on al fields. When trying to access this property, however, I get an error stating that this property does not exist on role field.

Curiously, somewhere else in my application, select_related works just as expected on document that has a ListField(ReferenceField(...)).

mongoengine version is 0.16.2

Does anyone see what I'm doing wrong?

Start with the User.role and User.project ReferenceField definitions and the shown User.objects(project=project_id).select_related() query. Compare scalar reference behavior with the ListField(ReferenceField(...)) case described in the issue. Done means selecting users dereferences the role and project fields as expected, while preserving the working list-reference behavior.