diff --git a/README b/README
old mode 100755
new mode 100644
index 1f6f71a..03d9a2a
--- a/README
+++ b/README
@@ -45,26 +45,23 @@ have an inner Meta class that inherits from ``Sortable.Meta``
             return self.title
 
 
-For models that you want sortable relative to a ``ForeignKey`` field, you need to
-specify a property: ``sortable_by`` that is equal to the class defined as your ForeignKey field.
-If you're upgrading from a version < 1.2, you do not need to redefine sortable_by.
-1.2 is backwards compatible to 1.0.
+It is also possible to order objects relative to another object that is a ForeignKey:
 
-    #admin.py
+    from adminsortable.fields import SortableForeignKey
+
+    #models.py
     class Category(models.Model):
         title = models.CharField(max_length=50)
         ...
     
-    class MySortableClass(Sortable):
+    class Project(Sortable):
         class Meta(Sortable.Meta)
         
-        category = models.ForeignKey(Category)
+        category = SortableForeignKey(Category)
         title = models.CharField(max_length=50)
         
         def __unicode__(self):
             return self.title
-        
-        sortable_by = Category
 
 
 Sortable has one field: `order` and adds a default ordering value set to `order`.
@@ -132,13 +129,10 @@ Status
 admin-sortable is currently used in production.
 
 
-What's new in 1.2
+What's new in 1.3
 =============
-- Refactored ``sortable_by`` to be a property rather than a classmethod, which is much less work to implement.
-- Fixed an issue with ordering which could result in sortable change list view objects not being grouped properly.
-- Refactored the ORM calls to determine if an object is sortable, and what the next order should be, to return
-scalar values and to not hydrate any objects whatsoever. This potentially decreases memory usage by exponential
-factors.
+- Refactored ``sortable_by`` to subclass ForeignKey rather than a property or classmethod.
+  No more extra property hackishness.
 
 Features
 =============
@@ -156,7 +150,6 @@ to the foreign key object if it also inherits from Sortable.
 Future
 ------
 - Support for foreign keys that are self referential
-- Support for ForeignKeys that have not been previously defined
 - More unit tests
 
 Requirements
diff --git a/adminsortable/__init__.py b/adminsortable/__init__.py
index 3cb15d8..7c4488d 100755
--- a/adminsortable/__init__.py
+++ b/adminsortable/__init__.py
@@ -1,4 +1,4 @@
-VERSION = (1, 2, 0, "f", 0)  # following PEP 386
+VERSION = (1, 3, "f", 0)  # following PEP 386
 DEV_N = None
 
 
@@ -7,7 +7,7 @@ def get_version():
     if VERSION[2]:
         version = "%s.%s" % (version, VERSION[2])
     if VERSION[3] != "f":
-        version = "%s%s%s" % (version, VERSION[3], VERSION[4])
+        version = "%s%s" % (version, VERSION[3])
         if DEV_N:
             version = "%s.dev%s" % (version, DEV_N)
     return version
diff --git a/adminsortable/admin.py b/adminsortable/admin.py
old mode 100755
new mode 100644
index 8097647..459042a
--- a/adminsortable/admin.py
+++ b/adminsortable/admin.py
@@ -9,6 +9,7 @@ from django.shortcuts import render
 from django.template.defaultfilters import capfirst
 from django.views.decorators.csrf import csrf_exempt
 
+from adminsortable.fields import SortableForeignKey
 from adminsortable.models import Sortable
 
 STATIC_URL = settings.STATIC_URL
@@ -20,8 +21,17 @@ class SortableAdmin(ModelAdmin):
     class Meta:
         abstract = True
 
+    def _get_sortable_foreign_key(self):
+        sortable_foreign_key = None
+        for field in self.model._meta.fields:
+            if isinstance(field, SortableForeignKey):
+                sortable_foreign_key = field
+                break
+        return sortable_foreign_key
+
     def __init__(self, *args, **kwargs):
         super(SortableAdmin, self).__init__(*args, **kwargs)
+
         self.has_sortable_tabular_inlines = False
         self.has_sortable_stacked_inlines = False
         for klass in self.inlines:
@@ -55,11 +65,16 @@ class SortableAdmin(ModelAdmin):
 
         #Determine if we need to regroup objects relative to a foreign key specified on the
         # model class that is extending Sortable.
-        sortable_by = getattr(self.model, 'sortable_by', None)
-        if sortable_by:
+        #Legacy support for 'sortable_by' defined as a model property
+        sortable_by_property = getattr(self.model, 'sortable_by', None)
+
+        #`sortable_by` defined as a SortableForeignKey
+        sortable_by_fk = self._get_sortable_foreign_key()
+
+        if sortable_by_property:
             #backwards compatibility for < 1.1.1, where sortable_by was a classmethod instead of a property
             try:
-                sortable_by_class, sortable_by_expression = sortable_by()
+                sortable_by_class, sortable_by_expression = sortable_by_property()
             except TypeError, ValueError:
                 sortable_by_class = self.model.sortable_by
                 sortable_by_expression = sortable_by_class.__name__.lower()
@@ -67,15 +82,24 @@ class SortableAdmin(ModelAdmin):
             sortable_by_class_display_name = sortable_by_class._meta.verbose_name_plural
             sortable_by_class_is_sortable = sortable_by_class.is_sortable()
 
+        elif sortable_by_fk:
+            #get sortable by properties from the SortableForeignKey field - supported in 1.3+
+            sortable_by_class_display_name = sortable_by_fk.rel.to._meta.verbose_name_plural
+            sortable_by_class = sortable_by_fk.rel.to
+            sortable_by_expression = sortable_by_fk.name.lower()
+            sortable_by_class_is_sortable = sortable_by_class.is_sortable()
+
+        else:
+            #model is not sortable by another model
+            sortable_by_class = sortable_by_expression = sortable_by_class_display_name =\
+            sortable_by_class_is_sortable = None
+
+        if sortable_by_property or sortable_by_fk:
             # Order the objects by the property they are sortable by, then by the order, otherwise the regroup
             # template tag will not show the objects correctly as
             # shown in https://docs.djangoproject.com/en/1.3/ref/templates/builtins/#regroup
             objects = objects.order_by(sortable_by_expression, 'order')
 
-        else:
-            sortable_by_class = sortable_by_expression = sortable_by_class_display_name =\
-            sortable_by_class_is_sortable = None
-
         try:
             verbose_name_plural = opts.verbose_name_plural.__unicode__()
         except AttributeError:
diff --git a/adminsortable/fields.py b/adminsortable/fields.py
new file mode 100644
index 0000000..e93f2bc
--- /dev/null
+++ b/adminsortable/fields.py
@@ -0,0 +1,18 @@
+from django.db.models.fields.related import ForeignKey
+
+
+class SortableForeignKey(ForeignKey):
+    """
+    Field simply acts as a flag to determine the class to sort by.
+    This field replaces previous functionality where `sortable_by` was definied as a model property
+    that specified another model class.
+    """
+
+    def south_field_triple(self):
+        try:
+            from south.modelsinspector import introspector
+            cls_name = '%s.%s' % (self.__class__.__module__ , self.__class__.__name__)
+            args, kwargs = introspector(self)
+            return cls_name, args, kwargs
+        except ImportError:
+            pass
diff --git a/adminsortable/models.py b/adminsortable/models.py
old mode 100755
new mode 100644
index af299de..8a94b3d
--- a/adminsortable/models.py
+++ b/adminsortable/models.py
@@ -1,6 +1,16 @@
 from django.contrib.contenttypes.models import ContentType
 from django.db import models
 
+from adminsortable.fields import SortableForeignKey
+
+
+class MultipleSortableForeignKeyException(Exception):
+    def __init__(self, value):
+        self.value = value
+
+    def __str__(self):
+        return repr(self.value)
+
 
 class Sortable(models.Model):
     """
@@ -18,7 +28,10 @@ class Sortable(models.Model):
     Override `sortable_by` method to make your model be sortable by a foreign key field.
     Set `sortable_by` to the class specified in the foreign key relationship.
     """
+
     order = models.PositiveIntegerField(editable=False, default=1, db_index=True)
+
+    #legacy support
     sortable_by = None
 
     class Meta:
@@ -37,6 +50,17 @@ class Sortable(models.Model):
     def model_type_id(cls):
         return ContentType.objects.get_for_model(cls).id
 
+    def __init__(self, *args, **kwargs):
+        super(Sortable, self).__init__(*args, **kwargs)
+
+        #Validate that model only contains at most one SortableForeignKey
+        sortable_foreign_keys = []
+        for field in self._meta.fields:
+            if isinstance(field, SortableForeignKey):
+                sortable_foreign_keys.append(field)
+        if len(sortable_foreign_keys) > 1:
+            raise MultipleSortableForeignKeyException(u'%s may only have one SortableForeignKey' % self)
+
     def save(self, *args, **kwargs):
         if not self.id:
             try:
diff --git a/adminsortable/templates/adminsortable/change_list.html b/adminsortable/templates/adminsortable/change_list.html
old mode 100755
new mode 100644
diff --git a/adminsortable/templates/adminsortable/shared/javascript_includes.html b/adminsortable/templates/adminsortable/shared/javascript_includes.html
old mode 100755
new mode 100644
diff --git a/adminsortable/templates/adminsortable/shared/nested_objects.html b/adminsortable/templates/adminsortable/shared/nested_objects.html
old mode 100755
new mode 100644
diff --git a/adminsortable/templatetags/django_template_additions.py b/adminsortable/templatetags/django_template_additions.py
old mode 100755
new mode 100644
diff --git a/sample_project/adminsortable.sqlite b/sample_project/adminsortable.sqlite
old mode 100755
new mode 100644
index 7df8bd7..87a2b3a
Binary files a/sample_project/adminsortable.sqlite and b/sample_project/adminsortable.sqlite differ
diff --git a/sample_project/app/admin.py b/sample_project/app/admin.py
old mode 100755
new mode 100644
index f365aab..a1eb445
--- a/sample_project/app/admin.py
+++ b/sample_project/app/admin.py
@@ -1,7 +1,7 @@
 from django.contrib import admin
 
 from adminsortable.admin import SortableAdmin, SortableTabularInline, SortableStackedInline
-from app.models import Category, Project, Credit, Note, Sample
+from app.models import Category, Project, Credit, Note
 
 
 admin.site.register(Category, SortableAdmin)
@@ -20,4 +20,3 @@ class ProjectAdmin(SortableAdmin):
     list_display = ['__unicode__', 'category']
 
 admin.site.register(Project, ProjectAdmin)
-admin.site.register(Sample, SortableAdmin)
diff --git a/sample_project/app/fixtures/initial_data.json b/sample_project/app/fixtures/initial_data.json
new file mode 100644
index 0000000..03bb2e0
--- /dev/null
+++ b/sample_project/app/fixtures/initial_data.json
@@ -0,0 +1,56 @@
+[
+    {
+        "pk": 1,
+        "model": "app.category",
+        "fields": {
+            "order": 1,
+            "title": "Test 1"
+        }
+    },
+    {
+        "pk": 2,
+        "model": "app.category",
+        "fields": {
+            "order": 2,
+            "title": "Test 2"
+        }
+    },
+    {
+        "pk": 3,
+        "model": "app.category",
+        "fields": {
+            "order": 3,
+            "title": "Test 3"
+        }
+    },
+    {
+        "pk": 1,
+        "model": "app.project",
+        "fields": {
+            "category": 1,
+            "description": "Test",
+            "order": 1,
+            "title": "Test Project 1"
+        }
+    },
+    {
+        "pk": 2,
+        "model": "app.project",
+        "fields": {
+            "category": 1,
+            "description": "Test",
+            "order": 2,
+            "title": "Test Project 2"
+        }
+    },
+    {
+        "pk": 3,
+        "model": "app.project",
+        "fields": {
+            "category": 2,
+            "description": "Test",
+            "order": 3,
+            "title": "Test Project 3"
+        }
+    }
+]
diff --git a/sample_project/app/migrations/0001_initial.py b/sample_project/app/migrations/0001_initial.py
deleted file mode 100644
index 099672b..0000000
--- a/sample_project/app/migrations/0001_initial.py
+++ /dev/null
@@ -1,77 +0,0 @@
-# encoding: utf-8
-import datetime
-from south.db import db
-from south.v2 import SchemaMigration
-from django.db import models
-
-class Migration(SchemaMigration):
-
-    def forwards(self, orm):
-        
-        # Adding model 'Category'
-        db.create_table('app_category', (
-            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
-            ('order', self.gf('django.db.models.fields.PositiveIntegerField')(default=1, db_index=True)),
-            ('title', self.gf('django.db.models.fields.CharField')(max_length=50)),
-        ))
-        db.send_create_signal('app', ['Category'])
-
-        # Adding model 'Project'
-        db.create_table('app_project', (
-            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
-            ('order', self.gf('django.db.models.fields.PositiveIntegerField')(default=1, db_index=True)),
-            ('title', self.gf('django.db.models.fields.CharField')(max_length=50)),
-            ('category', self.gf('django.db.models.fields.related.ForeignKey')(to=orm['app.Category'])),
-            ('description', self.gf('django.db.models.fields.TextField')()),
-        ))
-        db.send_create_signal('app', ['Project'])
-
-        # Adding model 'Credit'
-        db.create_table('app_credit', (
-            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
-            ('order', self.gf('django.db.models.fields.PositiveIntegerField')(default=1, db_index=True)),
-            ('project', self.gf('django.db.models.fields.related.ForeignKey')(to=orm['app.Project'])),
-            ('first_name', self.gf('django.db.models.fields.CharField')(max_length=30)),
-            ('last_name', self.gf('django.db.models.fields.CharField')(max_length=30)),
-        ))
-        db.send_create_signal('app', ['Credit'])
-
-
-    def backwards(self, orm):
-        
-        # Deleting model 'Category'
-        db.delete_table('app_category')
-
-        # Deleting model 'Project'
-        db.delete_table('app_project')
-
-        # Deleting model 'Credit'
-        db.delete_table('app_credit')
-
-
-    models = {
-        'app.category': {
-            'Meta': {'ordering': "['order', 'id']", 'object_name': 'Category'},
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'title': ('django.db.models.fields.CharField', [], {'max_length': '50'})
-        },
-        'app.credit': {
-            'Meta': {'ordering': "['order', 'id']", 'object_name': 'Credit'},
-            'first_name': ('django.db.models.fields.CharField', [], {'max_length': '30'}),
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'last_name': ('django.db.models.fields.CharField', [], {'max_length': '30'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'project': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['app.Project']"})
-        },
-        'app.project': {
-            'Meta': {'ordering': "['order', 'id']", 'object_name': 'Project'},
-            'category': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['app.Category']"}),
-            'description': ('django.db.models.fields.TextField', [], {}),
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'title': ('django.db.models.fields.CharField', [], {'max_length': '50'})
-        }
-    }
-
-    complete_apps = ['app']
diff --git a/sample_project/app/migrations/0002_add_note.py b/sample_project/app/migrations/0002_add_note.py
deleted file mode 100644
index 8952798..0000000
--- a/sample_project/app/migrations/0002_add_note.py
+++ /dev/null
@@ -1,59 +0,0 @@
-# encoding: utf-8
-import datetime
-from south.db import db
-from south.v2 import SchemaMigration
-from django.db import models
-
-class Migration(SchemaMigration):
-
-    def forwards(self, orm):
-        
-        # Adding model 'Note'
-        db.create_table('app_note', (
-            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
-            ('order', self.gf('django.db.models.fields.PositiveIntegerField')(default=1, db_index=True)),
-            ('project', self.gf('django.db.models.fields.related.ForeignKey')(to=orm['app.Project'])),
-            ('text', self.gf('django.db.models.fields.CharField')(max_length=100)),
-        ))
-        db.send_create_signal('app', ['Note'])
-
-
-    def backwards(self, orm):
-        
-        # Deleting model 'Note'
-        db.delete_table('app_note')
-
-
-    models = {
-        'app.category': {
-            'Meta': {'ordering': "['order', 'id']", 'object_name': 'Category'},
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'title': ('django.db.models.fields.CharField', [], {'max_length': '50'})
-        },
-        'app.credit': {
-            'Meta': {'ordering': "['order', 'id']", 'object_name': 'Credit'},
-            'first_name': ('django.db.models.fields.CharField', [], {'max_length': '30'}),
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'last_name': ('django.db.models.fields.CharField', [], {'max_length': '30'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'project': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['app.Project']"})
-        },
-        'app.note': {
-            'Meta': {'ordering': "['order', 'id']", 'object_name': 'Note'},
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'project': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['app.Project']"}),
-            'text': ('django.db.models.fields.CharField', [], {'max_length': '100'})
-        },
-        'app.project': {
-            'Meta': {'ordering': "['order', 'id']", 'object_name': 'Project'},
-            'category': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['app.Category']"}),
-            'description': ('django.db.models.fields.TextField', [], {}),
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'title': ('django.db.models.fields.CharField', [], {'max_length': '50'})
-        }
-    }
-
-    complete_apps = ['app']
diff --git a/sample_project/app/migrations/0003_add_sample.py b/sample_project/app/migrations/0003_add_sample.py
deleted file mode 100755
index 474c29e..0000000
--- a/sample_project/app/migrations/0003_add_sample.py
+++ /dev/null
@@ -1,68 +0,0 @@
-# encoding: utf-8
-import datetime
-from south.db import db
-from south.v2 import SchemaMigration
-from django.db import models
-
-class Migration(SchemaMigration):
-
-    def forwards(self, orm):
-        
-        # Adding model 'Sample'
-        db.create_table('app_sample', (
-            ('id', self.gf('django.db.models.fields.AutoField')(primary_key=True)),
-            ('order', self.gf('django.db.models.fields.PositiveIntegerField')(default=1, db_index=True)),
-            ('title', self.gf('django.db.models.fields.CharField')(max_length=50)),
-            ('category', self.gf('django.db.models.fields.related.ForeignKey')(to=orm['app.Category'])),
-            ('description', self.gf('django.db.models.fields.TextField')()),
-        ))
-        db.send_create_signal('app', ['Sample'])
-
-
-    def backwards(self, orm):
-        
-        # Deleting model 'Sample'
-        db.delete_table('app_sample')
-
-
-    models = {
-        'app.category': {
-            'Meta': {'ordering': "['order']", 'object_name': 'Category'},
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'title': ('django.db.models.fields.CharField', [], {'max_length': '50'})
-        },
-        'app.credit': {
-            'Meta': {'ordering': "['order']", 'object_name': 'Credit'},
-            'first_name': ('django.db.models.fields.CharField', [], {'max_length': '30'}),
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'last_name': ('django.db.models.fields.CharField', [], {'max_length': '30'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'project': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['app.Project']"})
-        },
-        'app.note': {
-            'Meta': {'ordering': "['order']", 'object_name': 'Note'},
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'project': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['app.Project']"}),
-            'text': ('django.db.models.fields.CharField', [], {'max_length': '100'})
-        },
-        'app.project': {
-            'Meta': {'ordering': "['order']", 'object_name': 'Project'},
-            'category': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['app.Category']"}),
-            'description': ('django.db.models.fields.TextField', [], {}),
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'title': ('django.db.models.fields.CharField', [], {'max_length': '50'})
-        },
-        'app.sample': {
-            'Meta': {'ordering': "['order']", 'object_name': 'Sample'},
-            'category': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['app.Category']"}),
-            'description': ('django.db.models.fields.TextField', [], {}),
-            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
-            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'}),
-            'title': ('django.db.models.fields.CharField', [], {'max_length': '50'})
-        }
-    }
-
-    complete_apps = ['app']
diff --git a/sample_project/app/migrations/__init__.py b/sample_project/app/migrations/__init__.py
deleted file mode 100644
index e69de29..0000000
diff --git a/sample_project/app/models.py b/sample_project/app/models.py
old mode 100755
new mode 100644
index 9b58536..489f257
--- a/sample_project/app/models.py
+++ b/sample_project/app/models.py
@@ -1,5 +1,6 @@
 from django.db import models
 
+from adminsortable.fields import SortableForeignKey
 from adminsortable.models import Sortable
 
 
@@ -25,34 +26,16 @@ class Category(SimpleModel, Sortable):
 
 
 #a model that is sortable relative to a foreign key that is also sortable
+#uses SortableForeignKey field. Works with versions 1.3+
 class Project(SimpleModel, Sortable):
     class Meta(Sortable.Meta):
         pass
 
-    #deprecated: shown for backward compatibility only. Reference class "Sample" for proper
-    # designation of `sortable_by` as a property
-    @classmethod
-    def sortable_by(cls):
-        return Category, 'category'
-
-    category = models.ForeignKey(Category)
+    category = SortableForeignKey(Category)
     description = models.TextField()
 
 
-#a model that is sortable relative to a foreign key that is also sortable
-class Sample(SimpleModel, Sortable):
-    class Meta(Sortable.Meta):
-        ordering = Sortable.Meta.ordering + ['category']
-
-    category = models.ForeignKey(Category)
-    description = models.TextField()
-
-    #field to define which foreign key the model is sortable by.
-    #works with versions > 1.1.1
-    sortable_by = Category
-
-
-#registered as a tabular inline on project
+#registered as a tabular inline on `Project`
 class Credit(Sortable):
     class Meta(Sortable.Meta):
         pass
@@ -65,7 +48,7 @@ class Credit(Sortable):
         return '%s %s' % (self.first_name, self.last_name)
 
 
-#registered as a stacked inline on project
+#registered as a stacked inline on `Project`
 class Note(Sortable):
     class Meta(Sortable.Meta):
         pass
diff --git a/sample_project/app/tests.py b/sample_project/app/tests.py
old mode 100755
new mode 100644
index a086099..c209125
--- a/sample_project/app/tests.py
+++ b/sample_project/app/tests.py
@@ -7,8 +7,14 @@ from django.db import models
 from django.test import TestCase
 from django.test.client import Client, RequestFactory
 
-from models import Sortable
-from app.models import Category
+from adminsortable.fields import SortableForeignKey
+from adminsortable.models import Sortable, MultipleSortableForeignKeyException
+from app.models import Category, Credit, Note
+
+
+class BadSortableModel(models.Model):
+    note = SortableForeignKey(Note)
+    credit = SortableForeignKey(Credit)
 
 
 class TestSortableModel(Sortable):
@@ -19,7 +25,6 @@ class TestSortableModel(Sortable):
 
 
 class SortableTestCase(TestCase):
-
     def setUp(self):
         self.client = Client()
         self.factory = RequestFactory()
diff --git a/sample_project/settings.py b/sample_project/settings.py
old mode 100755
new mode 100644