diff -r 597515fcb343 Lib/argparse.py
--- a/Lib/argparse.py	Sat Jan 21 23:17:25 2017 +0200
+++ b/Lib/argparse.py	Sun Jan 22 12:00:34 2017 +0800
@@ -182,7 +182,7 @@
         self._root_section = self._Section(self, None)
         self._current_section = self._root_section
 
-        self._whitespace_matcher = _re.compile(r'\s+')
+        self._whitespace_matcher = _re.compile(r'\s+', _re.ASCII)
         self._long_break_matcher = _re.compile(r'\n\n\n+')
 
     # ===============================
diff -r 597515fcb343 Lib/test/test_argparse.py
--- a/Lib/test/test_argparse.py	Sat Jan 21 23:17:25 2017 +0200
+++ b/Lib/test/test_argparse.py	Sun Jan 22 12:00:34 2017 +0800
@@ -1943,6 +1943,23 @@
               ++foo       foo help
             '''))
 
+    def test_help_non_breaking_spaces(self):
+        parser = ErrorRaisingArgumentParser(
+            prog='PROG', description='main description')
+        parser.add_argument(
+            "--non-breaking", action='store_false',
+            help='help message containing non-breaking spaces shall not '
+            'wrap\N{NO-BREAK SPACE}at non-breaking spaces')
+        self.assertEqual(parser.format_help(), textwrap.dedent('''\
+            usage: PROG [-h] [--non-breaking]
+
+            main description
+
+            optional arguments:
+              -h, --help      show this help message and exit
+              --non-breaking  help message containing non-breaking spaces shall not
+                              wrap\N{NO-BREAK SPACE}at non-breaking spaces
+        '''))
 
     def test_help_alternate_prefix_chars(self):
         parser = self._get_parser(prefix_chars='+:/')