Index: base.py
===================================================================
--- base.py	(revision 6941)
+++ base.py	(working copy)
@@ -40,8 +40,7 @@
 
         # Build complete list of parents
         for base in bases:
-            # TODO: Checking for the presence of '_meta' is hackish.
-            if '_meta' in dir(base):
+            if base is not Model and issubclass(base, Model):
                 new_class._meta.parents.append(base)
                 new_class._meta.parents.extend(base._meta.parents)