upsert_one() on a missing document does an insert, not considering default field values

mongoengine==0.24.2
pymongo[srv]==4.2.0
MongoDB 5.0

Persisting a document lacks fields defined in the Document class:

class MyDocument(Document):
    version = IntField(default=1)
    foo = StringField(required=True)
    bar = StringField(required=True)

Creating an instance when there is nothing to be updated yet, doesn't consider default field value it seems ( or my expectation of the "insert" functionality of "upsert_one" is plain wrong ):

MyDocument.objects({"foo":"Hello"}).upsert_one(foo="World",bar="ups")

Inspecting the collection I can find the new document instance, but it only has fields "foo" and "bar" but lacks "version" !?

Start with the QuerySet.upsert_one() entry point and reproduce the example using MongoEngine 0.24.2, PyMongo 4.2.0, and MongoDB 5.0. Compare the inserted document with the MyDocument default declaration; done means the behavior of upsert_one() on a missing document is defined and covered for the default version field.