diff -r 3d440ae207d9 Objects/codeobject.c
--- a/Objects/codeobject.c	Mon Oct 03 11:16:17 2016 -0700
+++ b/Objects/codeobject.c	Mon Oct 03 22:16:30 2016 +0300
@@ -21,7 +21,7 @@ all_name_chars(PyObject *o)
     static char ok_name_char[256];
     static unsigned char *name_chars = (unsigned char *)NAME_CHARS;
     PyUnicodeObject *u = (PyUnicodeObject *)o;
-    const unsigned char *s;
+    const unsigned char *s, *e;
 
     if (!PyUnicode_Check(o) || PyUnicode_READY(u) == -1 ||
         PyUnicode_MAX_CHAR_VALUE(u) >= 128)
@@ -33,7 +33,8 @@ all_name_chars(PyObject *o)
             ok_name_char[*p] = 1;
     }
     s = PyUnicode_1BYTE_DATA(u);
-    while (*s) {
+    e = s + PyUnicode_GET_LENGTH(u);
+    while (s != e) {
         if (ok_name_char[*s++] == 0)
             return 0;
     }