Index: Doc/library/sys.rst
===================================================================
--- Doc/library/sys.rst	(revision 66695)
+++ Doc/library/sys.rst	(working copy)
@@ -578,7 +578,15 @@
    :file:`/usr/include/dlfcn.h` using the :program:`h2py` script. Availability:
    Unix.
 
+.. function:: setfilesystemencoding(enc)
 
+   Set the encoding used when converting Python strings to file names to *enc*.
+   By default, Python tries to determine the encoding it should use automatically
+   on Unix; on Windows, it avoids such conversion completely. This function can
+   be used when Python's determination of the encoding needs to be overwritten,
+   e.g. when not all file names on disk can be decoded using the encoding that
+   Python had chosen.
+
 .. function:: setprofile(profilefunc)
 
    .. index::
Index: Python/bltinmodule.c
===================================================================
--- Python/bltinmodule.c	(revision 66695)
+++ Python/bltinmodule.c	(working copy)
@@ -15,6 +15,7 @@
    Don't forget to modify PyUnicode_DecodeFSDefault() if you touch any of the
    values for Py_FileSystemDefaultEncoding!
 */
+static PyObject *file_system_encoding = NULL;
 #if defined(MS_WINDOWS) && defined(HAVE_USABLE_WCHAR_T)
 const char *Py_FileSystemDefaultEncoding = "mbcs";
 const int Py_HasFileSystemDefaultEncoding = 1;
@@ -26,6 +27,24 @@
 const int Py_HasFileSystemDefaultEncoding = 0;
 #endif
 
+int
+_Py_SetFileSystemEncoding(PyObject *s)
+{
+	PyObject *defenc;
+	if (!PyUnicode_Check(s)) {
+		PyErr_BadInternalCall();
+		return -1;
+	}
+	defenc = _PyUnicode_AsDefaultEncodedString(s, NULL);
+	if (!defenc)
+		return -1;
+	Py_INCREF(s);
+	Py_FileSystemDefaultEncoding = PyBytes_AsString(defenc);
+	Py_XDECREF(file_system_encoding);
+	file_system_encoding = s;
+	return 0;
+}
+
 static PyObject *
 builtin___build_class__(PyObject *self, PyObject *args, PyObject *kwds)
 {
Index: Python/sysmodule.c
===================================================================
--- Python/sysmodule.c	(revision 66695)
+++ Python/sysmodule.c	(working copy)
@@ -216,7 +216,24 @@
 operating system filenames."
 );
 
+static PyObject *
+sys_setfilesystemencoding(PyObject *self, PyObject *args)
+{
+	PyObject *new_encoding;
+	if (!PyArg_ParseTuple(args, "U:setfilesystemencoding", &new_encoding))
+		return NULL;
+	if (_Py_SetFileSystemEncoding(new_encoding))
+		return NULL;
+	Py_INCREF(Py_None);
+	return Py_None;
+}
 
+PyDoc_STRVAR(setfilesystemencoding_doc,
+"setfilesystemencoding(string) -> None\n\
+\n\
+Set the encoding used to convert Unicode filenames in\n\
+operating system filenames."
+);
 
 static PyObject *
 sys_intern(PyObject *self, PyObject *args)
@@ -872,6 +889,8 @@
 #endif
 	{"setdefaultencoding", sys_setdefaultencoding, METH_VARARGS,
 	 setdefaultencoding_doc},
+	{"setfilesystemencoding", sys_setfilesystemencoding, METH_VARARGS,
+	 setfilesystemencoding_doc},
 	{"setcheckinterval",	sys_setcheckinterval, METH_VARARGS,
 	 setcheckinterval_doc},
 	{"getcheckinterval",	sys_getcheckinterval, METH_NOARGS,