diff -r f9dd607dc04c Python/ceval.c
--- a/Python/ceval.c	Tue Jan 03 02:01:42 2017 +0100
+++ b/Python/ceval.c	Tue Jan 03 02:08:01 2017 +0100
@@ -5009,12 +5009,14 @@ PyObject *
 _PyFunction_FastCallDict(PyObject *func, PyObject **args, Py_ssize_t nargs,
                          PyObject *kwargs)
 {
+    /* small stack allocated on the C stack to pass keyword arguments
+       (key+value pairs) */
+    PyObject *small_stack[_PY_FASTCALL_SMALL_STACK * 2];
     PyCodeObject *co = (PyCodeObject *)PyFunction_GET_CODE(func);
     PyObject *globals = PyFunction_GET_GLOBALS(func);
     PyObject *argdefs = PyFunction_GET_DEFAULTS(func);
     PyObject *kwdefs, *closure, *name, *qualname;
-    PyObject *kwtuple, **k;
-    PyObject **d;
+    PyObject **k, **d;
     Py_ssize_t nd, nk;
     PyObject *result;
 
@@ -5044,12 +5046,17 @@ PyObject *
     if (nk != 0) {
         Py_ssize_t pos, i;
 
-        kwtuple = PyTuple_New(2 * nk);
-        if (kwtuple == NULL) {
-            return NULL;
-        }
-
-        k = &PyTuple_GET_ITEM(kwtuple, 0);
+        if (nk <= (Py_ssize_t)Py_ARRAY_LENGTH(small_stack) / 2) {
+            k = small_stack;
+        }
+        else {
+            k = PyMem_Malloc((2 * nk) * sizeof(PyObject *));
+            if (k == NULL) {
+                PyErr_NoMemory();
+                return NULL;
+            }
+        }
+
         pos = i = 0;
         while (PyDict_Next(kwargs, &pos, &k[i], &k[i+1])) {
             /* We must hold strong references because keyword arguments can be
@@ -5062,7 +5069,6 @@ PyObject *
         nk = i / 2;
     }
     else {
-        kwtuple = NULL;
         k = NULL;
     }
 
@@ -5085,7 +5091,21 @@ PyObject *
                                       k, k + 1, nk, 2,
                                       d, nd, kwdefs,
                                       closure, name, qualname);
-    Py_XDECREF(kwtuple);
+
+    if (k != NULL) {
+        Py_ssize_t i;
+
+        for (i=0; i < nk * 2; ) {
+            Py_DECREF(k[i]);
+            Py_DECREF(k[i+1]);
+            i += 2;
+        }
+
+        if (k != small_stack) {
+            PyMem_Free(k);
+        }
+    }
+
     return result;
 }