From 9d125c9e797643fbe776114407da321560ef7ca2 Mon Sep 17 00:00:00 2001
From: Frank Battaglia <frank@franks-macbook-pro-wired.home>
Date: Sun, 23 Feb 2014 19:37:42 -0500
Subject: [PATCH] inherit parent Document type _auto_id_field value

---
 mongoengine/base/metaclasses.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mongoengine/base/metaclasses.py b/mongoengine/base/metaclasses.py
index ff5afddf..4b2e8b9b 100644
--- a/mongoengine/base/metaclasses.py
+++ b/mongoengine/base/metaclasses.py
@@ -359,7 +359,8 @@ class TopLevelDocumentMetaclass(DocumentMetaclass):
                     new_class.id = field
 
         # Set primary key if not defined by the document
-        new_class._auto_id_field = False
+        new_class._auto_id_field = getattr(parent_doc_cls,
+                                           '_auto_id_field', False)
         if not new_class._meta.get('id_field'):
             new_class._auto_id_field = True
             new_class._meta['id_field'] = 'id'