Django auto_now and auto_now_add

For Django 1.1.

I have this in my models.py:

class User(models.Model):
    created = models.DateTimeField(auto_now_add=True)
    modified = models.DateTimeField(auto_now=True)

When updating a row I get:

[Sun Nov 15 02:18:12 2009] [error] /home/ptarjan/projects/twitter-meme/django/db/backends/mysql/base.py:84: Warning: Column 'created' cannot be null
[Sun Nov 15 02:18:12 2009] [error]   return self.cursor.execute(query, args)

The relevant part of my database is:

  `created` datetime NOT NULL,
  `modified` datetime NOT NULL,

Is this cause for concern?

Side question: in my admin tool, those two fields aren’t showing up. Is that expected?