From 53b977127fe8192f8bdf6a400de81086e128e936 Mon Sep 17 00:00:00 2001
From: Benjamin Peterson <benjamin@python.org>
Date: Mon, 23 Apr 2012 11:50:47 -0400
Subject: [PATCH] don't make shared keys with dict subclasses

---
 Objects/dictobject.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 2e45c8d8fdd..2afbbaee503 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -3686,7 +3686,7 @@ _PyObjectDict_SetItem(PyTypeObject *tp, PyObject **dictptr,
             res = PyDict_SetItem(dict, key, value);
             if (cached != ((PyDictObject *)dict)->ma_keys) {
                 /* Either update tp->ht_cached_keys or delete it */
-                if (cached->dk_refcnt == 1) {
+                if (cached->dk_refcnt == 1 && PyDict_CheckExact(dict)) {
                     CACHED_KEYS(tp) = make_keys_shared(dict);
                     if (CACHED_KEYS(tp) == NULL)
                         return -1;