In [16]: newuser = User(username='test')

In [17]: newuser.save()

In [18]: newuser.pk
Out[18]: 2

In [19]: s = SpecialUserSerializer(data={'special_user': 2})

In [20]: s.is_valid()
Out[20]: True

In [21]: s.save()
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-21-8f3ac9140d38> in <module>()
----> 1 s.save()

/home/mmikofski_l/Documents/Projects/drf_onetoone_test/venv/local/lib/python2.7/site-packages/rest_framework/serializers.pyc in save(self, **kwargs)
    213             )
    214         else:
--> 215             self.instance = self.create(validated_data)
    216             assert self.instance is not None, (
    217                 '`create()` did not return an object instance.'

/home/mmikofski_l/Documents/Projects/drf_onetoone_test/venv/local/lib/python2.7/site-packages/rest_framework/serializers.pyc in create(self, validated_data)
    914
    915         try:
--> 916             instance = ModelClass.objects.create(**validated_data)
    917         except TypeError:
    918             tb = traceback.format_exc()

/home/mmikofski_l/Documents/Projects/drf_onetoone_test/venv/local/lib/python2.7/site-packages/django/db/models/manager.pyc in manager_method(self, *args, **kwargs)
     83         def create_method(name, method):
     84             def manager_method(self, *args, **kwargs):
---> 85                 return getattr(self.get_queryset(), name)(*args, **kwargs)
     86             manager_method.__name__ = method.__name__
     87             manager_method.__doc__ = method.__doc__

/home/mmikofski_l/Documents/Projects/drf_onetoone_test/venv/local/lib/python2.7/site-packages/django/db/models/query.pyc in create(self, **kwargs)
    390         and returning the created object.
    391         """
--> 392         obj = self.model(**kwargs)
    393         self._for_write = True
    394         obj.save(force_insert=True, using=self.db)

/home/mmikofski_l/Documents/Projects/drf_onetoone_test/venv/local/lib/python2.7/site-packages/django/db/models/base.pyc in __init__(self, *args, **kwargs)
    551                 # checked) by the RelatedObjectDescriptor.
    552                 if rel_obj is not _DEFERRED:
--> 553                     _setattr(self, field.name, rel_obj)
    554             else:
    555                 if val is not _DEFERRED:

/home/mmikofski_l/Documents/Projects/drf_onetoone_test/venv/local/lib/python2.7/site-packages/django/db/models/fields/related_descriptors.pyc in __set__(self, instance, value)
    214                     instance._meta.object_name,
    215                     self.field.name,
--> 216                     self.field.remote_field.model._meta.object_name,
    217                 )
    218             )

ValueError: Cannot assign "2": "SpecialUser.special_user" must be a "User" instance.

In [22]: s = SpecialUserSerializer(data={'special_user': {'username': 'newuser'}})

In [23]: s.is_valid()
Out[23]: False

In [24]: s.errors
Out[24]:
ReturnDict([('special_user',
             [u"'{'username': 'newuser'}' value must be an integer."])])

In [25]: