diff -r adfec512fb32 Lib/test/test_posix.py
--- a/Lib/test/test_posix.py	Sun Jun 02 12:00:45 2013 -0700
+++ b/Lib/test/test_posix.py	Mon Jun 03 15:14:06 2013 +0300
@@ -13,6 +13,7 @@
 import platform
 import pwd
 import shutil
+import socket
 import stat
 import tempfile
 import unittest
@@ -54,6 +55,30 @@
                 posix_func()
                 self.assertRaises(TypeError, posix_func, 1)
 
+    @unittest.skipUnless(hasattr(socket, 'sethostname'),
+                         "test needs socket.sethostname()")
+    def test_uname_result(self):
+        # issue #18109
+        # checking posix.uname_result for UnicodeDecodeError
+        # at invalid hostnames (by RFC952)
+        oldhn = socket.gethostname()
+        newhn = 'hât'
+        try:
+            socket.sethostname(newhn)
+        except OSError as e:
+            if e.errno == errno.EPERM:
+                self.skipTest("test should be run as root")
+            else:
+                raise
+
+        try:
+            self.assertEqual(posix.uname().nodename, newhn)
+        except UnicodeDecodeError:  # test failed, restore hostname
+            socket.sethostname(oldhn)
+            raise
+
+        socket.sethostname(oldhn)
+
     if hasattr(posix, 'getresuid'):
         def test_getresuid(self):
             user_ids = posix.getresuid()
diff -r adfec512fb32 Misc/ACKS
--- a/Misc/ACKS	Sun Jun 02 12:00:45 2013 -0700
+++ b/Misc/ACKS	Mon Jun 03 15:14:06 2013 +0300
@@ -66,6 +66,7 @@
 Jeff Balogh
 Manuel Balsera
 Matt Bandy
+Dmi Baranov
 Michael J. Barber
 Daniel Barclay
 Nicolas Bareil
diff -r adfec512fb32 Modules/posixmodule.c
--- a/Modules/posixmodule.c	Sun Jun 02 12:00:45 2013 -0700
+++ b/Modules/posixmodule.c	Mon Jun 03 15:14:06 2013 +0300
@@ -4257,7 +4257,7 @@
 
 #define SET(i, field) \
     { \
-    PyObject *o = PyUnicode_DecodeASCII(field, strlen(field), NULL); \
+    PyObject *o = PyUnicode_DecodeLocaleAndSize(field, strlen(field), NULL); \
     if (!o) { \
         Py_DECREF(value); \
         return NULL; \