Django: getting rid of circular dependency

I have two apps, `commonapp` and `app1`. Here's `commonapp/models.py`: ``` from django.db import models #from app1.models import SpecificFields # Create your models here. class CommonFields(models.Model): a = models.IntegerField(default = 0) class Meta: abstract = True class SomeFields(models.Model): # a = models.ForeignKey(SpecificFields) a = models.ForeignKey('app1.models.SpecificFields') ``` and here's `app1/models.py`: ``` from django.db import models from commonapp.models import CommonFields # Create your models here. class SpecificFields(CommonFields): a2 = models.IntegerField(default=0) ``` When I try to run the SQL from either `app1` or `commonapp`, I get the following error: ``` $ python manage.py sql commonapp CommandError: One or more models did not validate: commonapp.somefields: 'a' has a relation with model app1.models.SpecificFields, which has either not been installed or is abstract. ``` I realize this is an issue of a circular dependency. Others have suggested of specifying the path to a class as a string instead of the actual class, but that does not work. I also cannot specify a string as the base class name in the derived class. Is such a circular dependency possible without refactoring my models?