diff -r 18ed518d2eef Objects/dictobject.c
--- a/Objects/dictobject.c	Tue Nov 29 09:56:07 2016 +0200
+++ b/Objects/dictobject.c	Tue Nov 29 21:32:46 2016 +0900
@@ -468,27 +468,22 @@ static int
         assert(DKIX_DUMMY <= ix && ix <= usable);
     }
 
-    for (i=0; i < usable; i++) {
+    for (i=0; i < keys->dk_nentries; i++) {
         PyDictKeyEntry *entry = &entries[i];
         PyObject *key = entry->me_key;
 
-        if (key != NULL) {
-            if (PyUnicode_CheckExact(key)) {
-                Py_hash_t hash = ((PyASCIIObject *)key)->hash;
-                assert(hash != -1);
-                assert(entry->me_hash == hash);
-            }
-            else {
-                /* test_dict fails if PyObject_Hash() is called again */
-                assert(entry->me_hash != -1);
-            }
-            if (!splitted) {
-                assert(entry->me_value != NULL);
-            }
+        assert(key != NULL);
+        if (PyUnicode_CheckExact(key)) {
+            Py_hash_t hash = ((PyASCIIObject *)key)->hash;
+            assert(hash != -1);
+            assert(entry->me_hash == hash);
         }
-
-        if (splitted) {
-            assert(entry->me_value == NULL);
+        else {
+            /* test_dict fails if PyObject_Hash() is called again */
+            assert(entry->me_hash != -1);
+        }
+        if (!splitted) {
+            assert(entry->me_value != NULL);
         }
     }
 
@@ -505,7 +500,8 @@ static int
 #endif
 
 
-static PyDictKeysObject *new_keys_object(Py_ssize_t size)
+static PyDictKeysObject *
+new_keys_object(Py_ssize_t size)
 {
     PyDictKeysObject *dk;
     Py_ssize_t es, usable;
@@ -548,7 +544,9 @@ static PyDictKeysObject *new_keys_object
     dk->dk_lookup = lookdict_unicode_nodummy;
     dk->dk_nentries = 0;
     memset(&dk->dk_indices.as_1[0], 0xff, es * size);
-    memset(DK_ENTRIES(dk), 0, sizeof(PyDictKeyEntry) * usable);
+#if Py_DEBUG
+    memset(DK_ENTRIES(dk), 0xcc, sizeof(PyDictKeyEntry) * usable);
+#endif
     return dk;
 }
 
@@ -604,17 +602,14 @@ static PyObject *
 new_dict_with_shared_keys(PyDictKeysObject *keys)
 {
     PyObject **values;
-    Py_ssize_t i, size;
-
-    size = USABLE_FRACTION(DK_SIZE(keys));
+
+    Py_ssize_t size = USABLE_FRACTION(DK_SIZE(keys));
     values = new_values(size);
     if (values == NULL) {
         DK_DECREF(keys);
         return PyErr_NoMemory();
     }
-    for (i = 0; i < size; i++) {
-        values[i] = NULL;
-    }
+    memset(values, 0, sizeof(PyObject*)*size);
     return new_dict(keys, values);
 }
 
@@ -1092,7 +1087,6 @@ find_empty_slot(PyDictObject *mp, PyObje
     }
     ep = &ep0[mp->ma_keys->dk_nentries];
     *hashpos = i & mask;
-    assert(ep->me_value == NULL);
     *value_addr = &ep->me_value;
 }
 
@@ -1160,7 +1154,7 @@ insertdict(PyDictObject *mp, PyObject *k
         ep->me_key = key;
         ep->me_hash = hash;
         if (mp->ma_values) {
-            assert (mp->ma_values[mp->ma_keys->dk_nentries] == NULL);
+            ep->me_value = NULL;
             mp->ma_values[mp->ma_keys->dk_nentries] = value;
         }
         else {
@@ -1347,10 +1341,13 @@ make_keys_shared(PyObject *op)
                 "Not enough memory to allocate new values array");
             return NULL;
         }
-        for (i = 0; i < size; i++) {
+        for (i = 0; i < mp->ma_keys->dk_nentries; i++) {
             values[i] = ep0[i].me_value;
             ep0[i].me_value = NULL;
         }
+        for (; i < size; i++) {
+            values[i] = NULL;
+        }
         mp->ma_keys->dk_lookup = lookdict_split;
         mp->ma_values = values;
     }
@@ -2821,7 +2818,8 @@ PyDict_SetDefault(PyObject *d, PyObject 
         MAINTAIN_TRACKING(mp, key, value);
         ep->me_key = key;
         ep->me_hash = hash;
-        if (mp->ma_values) {
+        if (_PyDict_HasSplitTable(mp)) {
+            ep->me_value = NULL;
             assert(mp->ma_values[mp->ma_keys->dk_nentries] == NULL);
             mp->ma_values[mp->ma_keys->dk_nentries] = value;
         }