diff -r ab6f520f3637 Modules/readline.c
--- a/Modules/readline.c	Mon Sep 21 01:11:26 2015 -0400
+++ b/Modules/readline.c	Mon Sep 21 19:29:17 2015 +0300
@@ -464,10 +464,11 @@ set_completer_delims(PyObject *self, PyO
     /* Keep a reference to the allocated memory in the module state in case
        some other module modifies rl_completer_word_break_characters
        (see issue #17289). */
-    free(completer_word_break_characters);
-    completer_word_break_characters = strdup(break_chars);
-    if (completer_word_break_characters) {
-        rl_completer_word_break_characters = completer_word_break_characters;
+    break_chars = strdup(break_chars);
+    if (break_chars) {
+        free(completer_word_break_characters);
+        completer_word_break_characters = break_chars;
+        rl_completer_word_break_characters = break_chars;
         Py_RETURN_NONE;
     }
     else