"Ensure this value is greater than or equal to 0"

[olance]

I get this error from the Django Admin app, hosted on Google App Engine with Google Cloud SQL as a database backend.

Everything works perfectly well on my dev machine, and used to work on GAE too.
I can't figure out why I'm getting this error now, with any version string entered into the field...

any help/idea appreciated :)

[olance]

I have "fixed" the issue by changing the inheritance of VersionField from models.PositiveIntegerField to models.IntegerField.

It did the trick, but I really can't figure why validation are failing when everything seems to work correctly otherwise.