db.models.Model regression - can't override some methods

[Lucky]

I want to migrate my project from the django-1.1.2 to the django 1.2.3 and I have problem with custom model managers what overrides Manager.create() method. For example:

class Book(models.Model):
    title = models.CharField(max_length=10)
    author = models.ForeignKey(Author)
    objects = CustomManager()

class CustomManager(models.Manager):
    def create(self, **kwargs):
        # business logic here
        return super(CustomManager, self).create(**kwargs)

Django 1.2.3 uses the CustomManager.create() method on the 'objects' descriptor as expected.

Book.objects.create(author=a1, title='How to be smart')

In the django-1.1.2 the same behavior had related field 'book_set' descriptor .
But in the 1.2.3 CustomManager.create() does not called anymore on related field. The next code has different behavior:

author.book_set.create(title='How to program')

The difference in the implementation for create method in the RelatedManger class. In the 1.1.2 it was delegate result to the create() method of it superclass (CustomManager).

return super(RelatedManager, self).create(**kwargs)

​http://code.djangoproject.com/browser/django/tags/releases/1.1.2/django/db/models/fields/related.py#L367

But the 1.2. delegates result to the result of .using(db), what is not superclass, but QuerySet.

return super(RelatedManager, self).using(db).create(**kwargs)

​http://code.djangoproect.com/browser/django/trunk/django/db/models/fields/related.py#L423

Look for the actual test case in the attachement. I'm Sorry for my silly english.