diff -r ffc0840762e4 Python/Python-ast.c
--- a/Python/Python-ast.c	Wed Jan 25 00:30:04 2017 +0200
+++ b/Python/Python-ast.c	Wed Jan 25 21:20:29 2017 +0900
@@ -503,6 +503,9 @@ static char *withitem_fields[]={
     "optional_vars",
 };
 
+_Py_IDENTIFIER(_fields);
+_Py_IDENTIFIER(_attributes);
+
 
 typedef struct {
     PyObject_HEAD
@@ -532,7 +535,6 @@ ast_clear(AST_object *self)
 static int
 ast_type_init(PyObject *self, PyObject *args, PyObject *kw)
 {
-    _Py_IDENTIFIER(_fields);
     Py_ssize_t i, numfields = 0;
     int res = -1;
     PyObject *key, *value, *fields;
@@ -657,6 +659,8 @@ static PyTypeObject AST_type = {
 
 static PyTypeObject* make_type(char *type, PyTypeObject* base, char**fields, int num_fields)
 {
+    _Py_IDENTIFIER(__module__);
+    _Py_IDENTIFIER(_ast);
     PyObject *fnames, *result;
     int i;
     fnames = PyTuple_New(num_fields);
@@ -669,8 +673,11 @@ static PyTypeObject* make_type(char *typ
         }
         PyTuple_SET_ITEM(fnames, i, field);
     }
-    result = PyObject_CallFunction((PyObject*)&PyType_Type, "s(O){sOss}",
-                    type, base, "_fields", fnames, "__module__", "_ast");
+    result = PyObject_CallFunction((PyObject*)&PyType_Type, "s(O){OOOO}",
+                    type, base,
+                    _PyUnicode_FromId(&PyId__fields), fnames,
+                    _PyUnicode_FromId(&PyId___module__),
+                    _PyUnicode_FromId(&PyId__ast));
     Py_DECREF(fnames);
     return (PyTypeObject*)result;
 }
@@ -678,7 +685,6 @@ static PyTypeObject* make_type(char *typ
 static int add_attributes(PyTypeObject* type, char**attrs, int num_fields)
 {
     int i, result;
-    _Py_IDENTIFIER(_attributes);
     PyObject *s, *l = PyTuple_New(num_fields);
     if (!l)
         return 0;
@@ -824,8 +830,8 @@ static int add_ast_fields(void)
     d = AST_type.tp_dict;
     empty_tuple = PyTuple_New(0);
     if (!empty_tuple ||
-        PyDict_SetItemString(d, "_fields", empty_tuple) < 0 ||
-        PyDict_SetItemString(d, "_attributes", empty_tuple) < 0) {
+        _PyDict_SetItemId(d, &PyId__fields, empty_tuple) < 0 ||
+        _PyDict_SetItemId(d, &PyId__attributes, empty_tuple) < 0) {
         Py_XDECREF(empty_tuple);
         return -1;
     }