diff -r 6c5f9c6c25ea Lib/test/test_dict.py
--- a/Lib/test/test_dict.py	Wed Sep 14 18:17:32 2016 +0300
+++ b/Lib/test/test_dict.py	Thu Sep 15 05:05:54 2016 +0900
@@ -839,83 +839,6 @@
             pass
         self._tracked(MyDict())
 
-    def make_shared_key_dict(self, n):
-        class C:
-            pass
-
-        dicts = []
-        for i in range(n):
-            a = C()
-            a.x, a.y, a.z = 1, 2, 3
-            dicts.append(a.__dict__)
-
-        return dicts
-
-    @support.cpython_only
-    def test_splittable_del(self):
-        """split table must be combined when del d[k]"""
-        a, b = self.make_shared_key_dict(2)
-
-        orig_size = sys.getsizeof(a)
-
-        del a['y']  # split table is combined
-        with self.assertRaises(KeyError):
-            del a['y']
-
-        self.assertGreater(sys.getsizeof(a), orig_size)
-        self.assertEqual(list(a), ['x', 'z'])
-        self.assertEqual(list(b), ['x', 'y', 'z'])
-
-        # Two dicts have different insertion order.
-        a['y'] = 42
-        self.assertEqual(list(a), ['x', 'z', 'y'])
-        self.assertEqual(list(b), ['x', 'y', 'z'])
-
-    @support.cpython_only
-    def test_splittable_pop(self):
-        """split table must be combined when d.pop(k)"""
-        a, b = self.make_shared_key_dict(2)
-
-        orig_size = sys.getsizeof(a)
-
-        a.pop('y')  # split table is combined
-        with self.assertRaises(KeyError):
-            a.pop('y')
-
-        self.assertGreater(sys.getsizeof(a), orig_size)
-        self.assertEqual(list(a), ['x', 'z'])
-        self.assertEqual(list(b), ['x', 'y', 'z'])
-
-        # Two dicts have different insertion order.
-        a['y'] = 42
-        self.assertEqual(list(a), ['x', 'z', 'y'])
-        self.assertEqual(list(b), ['x', 'y', 'z'])
-
-    @support.cpython_only
-    def test_splittable_pop_pending(self):
-        """pop a pending key in a splitted table should not crash"""
-        a, b = self.make_shared_key_dict(2)
-
-        a['a'] = 4
-        with self.assertRaises(KeyError):
-            b.pop('a')
-
-    @support.cpython_only
-    def test_splittable_popitem(self):
-        """split table must be combined when d.popitem()"""
-        a, b = self.make_shared_key_dict(2)
-
-        orig_size = sys.getsizeof(a)
-
-        item = a.popitem()  # split table is combined
-        self.assertEqual(item, ('z', 3))
-        with self.assertRaises(KeyError):
-            del a['z']
-
-        self.assertGreater(sys.getsizeof(a), orig_size)
-        self.assertEqual(list(a), ['x', 'y'])
-        self.assertEqual(list(b), ['x', 'y', 'z'])
-
     def test_iterator_pickling(self):
         for proto in range(pickle.HIGHEST_PROTOCOL + 1):
             data = {1:"a", 2:"b", 3:"c"}
diff -r 6c5f9c6c25ea Objects/dictobject.c
--- a/Objects/dictobject.c	Wed Sep 14 18:17:32 2016 +0300
+++ b/Objects/dictobject.c	Thu Sep 15 05:05:54 2016 +0900
@@ -388,7 +388,7 @@
  * This can be used to reserve enough size to insert n entries without
  * resizing.
  */
-#define ESTIMATE_SIZE(n)  (((n)*3) >> 1)
+#define ESTIMATE_SIZE(n)  (((n)*3+1) >> 1)
 
 /* Alternative fraction that is otherwise close enough to 2n/3 to make
  * little difference. 8 * 2/3 == 8 * 5/8 == 5. 16 * 2/3 == 16 * 5/8 == 10.
@@ -1236,16 +1236,16 @@
 but can be resplit by make_keys_shared().
 */
 static int
-dictresize(PyDictObject *mp, Py_ssize_t minused)
+dictresize(PyDictObject *mp, Py_ssize_t minsize)
 {
     Py_ssize_t i, newsize;
     PyDictKeysObject *oldkeys;
     PyObject **oldvalues;
     PyDictKeyEntry *ep0;
 
-    /* Find the smallest table size > minused. */
+    // Find the smallest table size >= minsize.
     for (newsize = PyDict_MINSIZE;
-         newsize <= minused && newsize > 0;
+         newsize < minsize && newsize > 0;
          newsize <<= 1)
         ;
     if (newsize <= 0) {
@@ -4229,9 +4229,11 @@
                 CACHED_KEYS(tp) = NULL;
                 DK_DECREF(cached);
             }
-        } else {
+        }
+        else {
+            int shared = cached == ((PyDictObject *)dict)->ma_keys;
             res = PyDict_SetItem(dict, key, value);
-            if (cached != ((PyDictObject *)dict)->ma_keys) {
+            if (shared && cached != ((PyDictObject *)dict)->ma_keys) {
                 /* Either update tp->ht_cached_keys or delete it */
                 if (cached->dk_refcnt == 1) {
                     CACHED_KEYS(tp) = make_keys_shared(dict);