`switch_db` does not dereference properly

I found switch_db functionality really handy and decided to tried it out this weekend. The problem is that it seems ReferenceFields are not properly resolved while in switch_db context. Here is what I've tried so far:

class Agency(DocumentModel):
    agency_id = db.StringField()
    name = db.StringField()
    url = db.StringField()
    timezone = db.StringField()
    lang = db.StringField()
    phone = db.StringField()
    fare_url = db.StringField()

class Route(DocumentModel):
    agency = db.ReferenceField(Agency)
    route_id = db.StringField()
    short_name = db.StringField()
    long_name = db.StringField()
    route_type = db.StringField()
    desc = db.StringField()
    url = db.StringField()
    color = db.StringField()
    text_color = db.StringField()

def route(self, route_id):
    with switch_db(document_models.Route, self.db_name()) as Route:
        route = Route.objects.get(route_id=route_id)
        assert (isinstance(route.agency, document_models.Agency))
        return route

The assertion fails as route.agency returns a Dbref. However, if I remove completely swith_db and setup the initial database as self.db_name(), everything works as expected.

def route(self, route_id):
    route = document_models.Route.objects.get(route_id=route_id)
    assert (isinstance(route.agency, document_models.Agency))
    return route

I even tried several other cases, with and without select_related(). No luck.

Start by reproducing the issue with the shown Agency and Route models, using switch_db and a ReferenceField, then trace how ReferenceField dereferencing behaves inside that context. Done means route.agency resolves to an Agency instance under switch_db, while the non-switch_db behavior and select_related cases remain correct.