sequelize adapter: Returns an object with undefined _id if idField is not explicitly set

[Floha258]

If you do not explicitly set the idField in a db service's settings, the sequelize adapter (I only know of sequelize doing this, maybe other adapters have the same behavior) returns an object, that has the _id field set explictly to undefined.
Is this wanted or an oversight?

[icebob]

Because the default id field name is id in sequelize adapter.