Ensure object_to is updated from self if required

Author: KevinGrahamFoster

AUTHORS.rst

@@ -40,6 +40,7 @@ Authors
 - Michael England
 - Gregory Bataille
 - Jesse Shapiro
+- Kevin Foster
 
 Background
 ==========

CHANGES.rst

@@ -5,6 +5,7 @@ Unreleased
 ----------
 - Use get_queryset rather than model.objects in history_view. (gh-303)
 - Change ugettext calls in models.py to ugettext_lazy
+- Resolve issue where model references itself (gh-278)
 
 1.9.0 (2017-06-11)
 ------------------

simple_history/models.py

@@ -172,8 +172,17 @@ def copy_fields(self, model):
                     field_arguments['to_field'] = old_field.to_fields[0]
                 if getattr(old_field, 'db_column', None):
                     field_arguments['db_column'] = old_field.db_column
+
+                # If old_field.rel.to is 'self' then we have a case where object has a foreign key
+                # to itself. In this case we update need to set the `to` value of the field
+                # to be set to a model. We can use the old_field.model value.
+                if isinstance(old_field.rel.to, str) and old_field.rel.to == 'self':
+                    object_to = old_field.model
+                else:
+                    object_to = old_field.rel.to
+
                 field = FieldType(
-                    old_field.rel.to,
+                    object_to,
                     related_name='+',
                     null=True,
                     blank=True,