diff -r a5e52b7be71f Objects/dictobject.c
--- a/Objects/dictobject.c	Fri Nov 04 16:34:46 2016 +0900
+++ b/Objects/dictobject.c	Fri Nov 18 19:55:37 2016 +0900
@@ -388,7 +388,7 @@ dk_set_index(PyDictKeysObject *keys, Py_
  * 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.
@@ -1355,10 +1355,11 @@ make_keys_shared(PyObject *op)
 PyObject *
 _PyDict_NewPresized(Py_ssize_t minused)
 {
+    Py_ssize_t minsize = ESTIMATE_SIZE(minused);
     Py_ssize_t newsize;
     PyDictKeysObject *new_keys;
     for (newsize = PyDict_MINSIZE;
-         newsize <= minused && newsize > 0;
+         newsize < minsize && newsize > 0;
          newsize <<= 1)
         ;
     new_keys = new_keys_object(newsize);