diff -r 2b9e5cbdb0b1 Objects/dictobject.c
--- a/Objects/dictobject.c	Thu Feb 02 19:25:24 2017 +0000
+++ b/Objects/dictobject.c	Sun Feb 05 13:12:11 2017 +0900
@@ -3890,26 +3890,28 @@
             if (dict == NULL)
                 return -1;
             *dictptr = dict;
         }
         if (value == NULL) {
             res = PyDict_DelItem(dict, key);
-            if (cached != ((PyDictObject *)dict)->ma_keys) {
+            if (cached != ((PyDictObject *)dict)->ma_keys &&
+                    cached == CACHED_KEYS(tp)) {
                 CACHED_KEYS(tp) = NULL;
                 DK_DECREF(cached);
             }
         }
         else {
             int was_shared = cached == ((PyDictObject *)dict)->ma_keys;
             res = PyDict_SetItem(dict, key, value);
             /* PyDict_SetItem() may call dictresize() and convert split table
              * into combined table.  In such case, convert it to split
              * table again and update type's shared key only when this is
              * the only dict sharing key with the type.
              */
-            if (was_shared && cached != ((PyDictObject *)dict)->ma_keys) {
+            if (was_shared && cached != ((PyDictObject *)dict)->ma_keys &&
+                    cached == CACHED_KEYS(tp)) {
                 if (cached->dk_refcnt == 1) {
                     CACHED_KEYS(tp) = make_keys_shared(dict);
                 } else {
                     CACHED_KEYS(tp) = NULL;
                 }
                 DK_DECREF(cached);