I have this model I\'m showing in the admin page:
class Dog(models.Model): bark_volume = models.DecimalField(... unladen_speed = models.DecimalField(...
OK, I figured it out from this answer.
You have to do something like this:
class Dog(models.Model): bark_volume = models.DecimalField(... unladen_speed = models.DecimalField(... def clean_fields(self): if self.bark_volume < 5: raise ValidationError({'bark_volume': ["Must be louder!",]})