diff --git a/Lib/test/test_codecs.py b/Lib/test/test_codecs.py
index 6706507..5a3834d 100644
--- a/Lib/test/test_codecs.py
+++ b/Lib/test/test_codecs.py
@@ -1516,6 +1516,34 @@
         self.assertEquals(codecs.raw_unicode_escape_decode(r"\u1234"), ("\u1234", 6))
         self.assertEquals(codecs.raw_unicode_escape_decode(br"\u1234"), ("\u1234", 6))
 
+class Utf8bTest(unittest.TestCase):
+
+    def test_utf8(self):
+        # Bad byte
+        self.assertEqual(b"foo\x80bar".decode("utf-8", "utf8b"),
+                         "foo\udc80bar")
+        self.assertEqual("foo\udc80bar".encode("utf-8", "utf8b"),
+                         b"foo\x80bar")
+        # bad-utf-8 encoded surrogate
+        self.assertEqual(b"\xed\xb0\x80".decode("utf-8", "utf8b"),
+                         "\udced\udcb0\udc80")
+        self.assertEqual("\udced\udcb0\udc80".encode("utf-8", "utf8b"),
+                         b"\xed\xb0\x80")
+
+    def test_ascii(self):
+        # bad byte
+        self.assertEqual(b"foo\x80bar".decode("ascii", "utf8b"),
+                         "foo\udc80bar")
+        self.assertEqual("foo\udc80bar".encode("ascii", "utf8b"),
+                         b"foo\x80bar")
+
+    def test_charmap(self):
+        # bad byte: \xa5 is unmapped in iso-8859-3
+        self.assertEqual(b"foo\xa5bar".decode("iso-8859-3", "utf8b"),
+                         "foo\udca5bar")
+        self.assertEqual("foo\udca5bar".encode("iso-8859-3", "utf8b"),
+                         b"foo\xa5bar")
+
 
 def test_main():
     support.run_unittest(
@@ -1543,6 +1571,7 @@
         CharmapTest,
         WithStmtTest,
         TypesTest,
+        Utf8bTest,
     )
 
 
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index 91e0432..a380505 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -7,6 +7,7 @@
 import unittest
 import warnings
 import sys
+import shutil
 from test import support
 
 # Tests creating TESTFN
@@ -698,9 +699,44 @@
                     self.assertRaises(os.error, os.setregid, 0, 0)
                 self.assertRaises(OverflowError, os.setregid, 1<<32, 0)
                 self.assertRaises(OverflowError, os.setregid, 0, 1<<32)
+
+    class Pep383Tests(unittest.TestCase):
+        filenames = [b'foo\xf6bar', 'foo\xf6bar'.encode("utf-8")]
+
+        def setUp(self):
+            self.fsencoding = sys.getfilesystemencoding()
+            sys.setfilesystemencoding("utf-8")
+            self.dir = support.TESTFN
+            self.bdir = self.dir.encode("utf-8", "utf8b")
+            os.mkdir(self.dir)
+            self.unicodefn = []
+            for fn in self.filenames:
+                f = open(os.path.join(self.bdir, fn), "w")
+                f.close()
+                self.unicodefn.append(fn.decode("utf-8", "utf8b"))
+
+        def tearDown(self):
+            shutil.rmtree(self.dir)
+            sys.setfilesystemencoding(self.fsencoding)
+
+        def test_listdir(self):
+            expected = set(self.unicodefn)
+            found = set(os.listdir(support.TESTFN))
+            self.assertEquals(found, expected)
+
+        def test_open(self):
+            for fn in self.unicodefn:
+                f = open(os.path.join(self.dir, fn))
+                f.close()
+
+        def test_stat(self):
+            for fn in self.unicodefn:
+                os.stat(os.path.join(self.dir, fn))
 else:
     class PosixUidGidTests(unittest.TestCase):
         pass
+    class Pep383Tests(unittest.TestCase):
+        pass
 
 def test_main():
     support.run_unittest(
@@ -714,7 +750,8 @@
         ExecTests,
         Win32ErrorTests,
         TestInvalidFD,
-        PosixUidGidTests
+        PosixUidGidTests,
+        Pep383Tests
     )
 
 if __name__ == "__main__":