Index: Lib/argparse.py
===================================================================
--- Lib/argparse.py	(revision 83761)
+++ Lib/argparse.py	(working copy)
@@ -75,6 +75,7 @@
 ]
 
 
+import collections as _collections
 import copy as _copy
 import os as _os
 import re as _re
@@ -1023,7 +1024,7 @@
 
         self._prog_prefix = prog
         self._parser_class = parser_class
-        self._name_parser_map = {}
+        self._name_parser_map = _collections.OrderedDict()
         self._choices_actions = []
 
         super(_SubParsersAction, self).__init__(