diff -r 3e897eef0fac Lib/argparse.py
--- a/Lib/argparse.py	Wed Mar 02 19:40:50 2016 +0200
+++ b/Lib/argparse.py	Sat Mar 05 19:44:17 2016 +0200
@@ -1172,17 +1172,21 @@
         # the special argument "-" means sys.std{in,out}
         if string == '-':
             if 'r' in self._mode:
-                return _sys.stdin
+                file = _sys.stdin.fileno()
             elif 'w' in self._mode:
-                return _sys.stdout
+                file = _sys.stdout.fileno()
             else:
                 msg = _('argument "-" with mode %r') % self._mode
                 raise ValueError(msg)
+            closefd = False
+        else:
+            file = string
+            closefd = True
 
         # all other arguments are used as file names
         try:
-            return open(string, self._mode, self._bufsize, self._encoding,
-                        self._errors)
+            return open(file, self._mode, self._bufsize, self._encoding,
+                        self._errors, closefd=closefd)
         except OSError as e:
             message = _("can't open '%s': %s")
             raise ArgumentTypeError(message % (string, e))
diff -r 3e897eef0fac Lib/test/test_argparse.py
--- a/Lib/test/test_argparse.py	Wed Mar 02 19:40:50 2016 +0200
+++ b/Lib/test/test_argparse.py	Sat Mar 05 19:44:17 2016 +0200
@@ -16,7 +16,13 @@
 from test import support
 from unittest import mock
 class StdIOBuffer(StringIO):
-    pass
+
+    def __init__(self, fileno=None):
+        self._real_fileno = fileno
+        super().__init__()
+
+    def fileno(self):
+        return self._real_fileno
 
 class TestCase(unittest.TestCase):
 
@@ -91,16 +97,11 @@
     # use it as the ArgumentParserError message
     old_stdout = sys.stdout
     old_stderr = sys.stderr
-    sys.stdout = StdIOBuffer()
-    sys.stderr = StdIOBuffer()
+    sys.stdout = StdIOBuffer(sys.stdout.fileno())
+    sys.stderr = StdIOBuffer(sys.stderr.fileno())
     try:
         try:
             result = parse_args(*args, **kwargs)
-            for key in list(vars(result)):
-                if getattr(result, key) is sys.stdout:
-                    setattr(result, key, old_stdout)
-                if getattr(result, key) is sys.stderr:
-                    setattr(result, key, old_stderr)
             return result
         except SystemExit:
             code = sys.exc_info()[1].code
@@ -1477,6 +1478,19 @@
         return self.name == other.name == text
 
 
+class FilenoMode(object):
+
+    def __init__(self, file, mode):
+        self.fileno = file.fileno()
+        self.mode = mode
+
+    def __eq__(self, other):
+        return self.fileno == other.fileno() and self.mode == other.mode
+
+    def __repr__(self):
+        return "FilenoMode({}, {!r})".format(self.fileno, self.mode)
+
+
 class TestFileTypeR(TempDirMixin, ParserTestCase):
     """Test the FileType option/argument type for reading files"""
 
@@ -1497,7 +1511,8 @@
         ('foo', NS(x=None, spam=RFile('foo'))),
         ('-x foo bar', NS(x=RFile('foo'), spam=RFile('bar'))),
         ('bar -x foo', NS(x=RFile('foo'), spam=RFile('bar'))),
-        ('-x - -', NS(x=sys.stdin, spam=sys.stdin)),
+        ('-x - -', NS(x=FilenoMode(sys.stdin, 'r'),
+                      spam=FilenoMode(sys.stdin, 'r'))),
         ('readonly', NS(x=None, spam=RFile('readonly'))),
     ]
 
@@ -1537,7 +1552,8 @@
         ('foo', NS(x=None, spam=RFile('foo'))),
         ('-x foo bar', NS(x=RFile('foo'), spam=RFile('bar'))),
         ('bar -x foo', NS(x=RFile('foo'), spam=RFile('bar'))),
-        ('-x - -', NS(x=sys.stdin, spam=sys.stdin)),
+        ('-x - -', NS(x=FilenoMode(sys.stdin, 'rb'),
+                      spam=FilenoMode(sys.stdin, 'rb'))),
     ]
 
 
@@ -1576,7 +1592,8 @@
         ('foo', NS(x=None, spam=WFile('foo'))),
         ('-x foo bar', NS(x=WFile('foo'), spam=WFile('bar'))),
         ('bar -x foo', NS(x=WFile('foo'), spam=WFile('bar'))),
-        ('-x - -', NS(x=sys.stdout, spam=sys.stdout)),
+        ('-x - -', NS(x=FilenoMode(sys.stdout, 'w'),
+                      spam=FilenoMode(sys.stdout, 'w'))),
     ]
 
 
@@ -1591,7 +1608,8 @@
         ('foo', NS(x=None, spam=WFile('foo'))),
         ('-x foo bar', NS(x=WFile('foo'), spam=WFile('bar'))),
         ('bar -x foo', NS(x=WFile('foo'), spam=WFile('bar'))),
-        ('-x - -', NS(x=sys.stdout, spam=sys.stdout)),
+        ('-x - -', NS(x=FilenoMode(sys.stdout, 'wb'),
+                      spam=FilenoMode(sys.stdout, 'wb'))),
     ]
 
 
@@ -1601,16 +1619,16 @@
     def test_open_args(self):
         FT = argparse.FileType
         cases = [
-            (FT('rb'), ('rb', -1, None, None)),
-            (FT('w', 1), ('w', 1, None, None)),
-            (FT('w', errors='replace'), ('w', -1, None, 'replace')),
-            (FT('wb', encoding='big5'), ('wb', -1, 'big5', None)),
-            (FT('w', 0, 'l1', 'strict'), ('w', 0, 'l1', 'strict')),
+            (FT('rb'), ('rb', -1, None, None), {"closefd": True}),
+            (FT('w', 1), ('w', 1, None, None), {"closefd": True}),
+            (FT('w', errors='replace'), ('w', -1, None, 'replace'), {"closefd": True}),
+            (FT('wb', encoding='big5'), ('wb', -1, 'big5', None), {"closefd": True}),
+            (FT('w', 0, 'l1', 'strict'), ('w', 0, 'l1', 'strict'), {"closefd": True}),
         ]
         with mock.patch('builtins.open') as m:
-            for type, args in cases:
+            for type, args, kwargs in cases:
                 type('foo')
-                m.assert_called_with('foo', *args)
+                m.assert_called_with('foo', *args, **kwargs)
 
 
 class TestTypeCallable(ParserTestCase):