foo.diff

diff --git a/django/db/migrations/state.py b/django/db/migrations/state.py
index 79a4411..ad9fb07 100644
--- a/django/db/migrations/state.py
+++ b/django/db/migrations/state.py
@@ -1,3 +1,5 @@
+from collections import OrderedDict
+
 from django.apps import AppConfig
 from django.apps.registry import Apps
 from django.db import models
@@ -151,6 +153,23 @@ class ModelState(object):
                     options[name] = set(normalize_together(it))
                 else:
                     options[name] = model._meta.original_attrs[name]
+
+        def flatten_bases(model):
+            bases = []
+            for base in model.__bases__:
+                if hasattr(base, "_meta") and base._meta.abstract:
+                    bases.extend(flatten_bases(base))
+                else:
+                    bases.append(base)
+            return bases
+
+        # We can't rely on __mro__ directly because we only want to flatten
+        # abstract models and not the whole tree. However by recursing on
+        # __bases__ we may end up with duplicates and ordering issues, we
+        # therefore discard any duplicates and reorder the bases according
+        # to their index in the MRO.
+        flattened_bases = sorted(list(set(flatten_bases(model))), key=lambda x:model.__mro__.index(x))
+
         # Make our record
         bases = tuple(
             (
@@ -158,8 +177,7 @@ class ModelState(object):
                 if hasattr(base, "_meta") else
                 base
             )
-            for base in model.__bases__
-#            if (not hasattr(base, "_meta") or not base._meta.abstract)
+            for base in flattened_bases
         )
         # Ensure at least one base inherits from models.Model
         if not any((isinstance(base, six.string_types) or issubclass(base, models.Model)) for base in bases):