potential django bug

bug.py

# found by frequant on #django

class BaseRatingModel(models.Model):
    """
    Base rating model
    """
    content_type = models.ForeignKey(ContentType)
    object_id = models.PositiveIntegerField()
    content_object = generic.GenericForeignKey()
    user = models.ForeignKey(settings.AUTH_USER_MODEL)
 
    class Meta:
        abstract = True
        unique_together = (('content_type', 'object_id', 'user'),)
 
 
class Helpful(BaseRatingModel):
    """
    Model for registering helpful votes
    """
    rating = models.SmallIntegerField(_('helpful'), choices=CHOICES)
 
# Then, if I create two Helpful objects for the same content_object, no errors are thrown