Index: Python/pythonrun.c
===================================================================
--- Python/pythonrun.c	(révision 81227)
+++ Python/pythonrun.c	(copie de travail)
@@ -712,8 +712,8 @@
     PyErr_Clear();
     fprintf(stderr,
             "Unable to get the locale encoding: "
-            "fallback to utf-8\n");
-    Py_FileSystemDefaultEncoding = "utf-8";
+            "fallback to ascii\n");
+    Py_FileSystemDefaultEncoding = "ascii";
     Py_HasFileSystemDefaultEncoding = 1;
 #endif
 
Index: Python/bltinmodule.c
===================================================================
--- Python/bltinmodule.c	(révision 81227)
+++ Python/bltinmodule.c	(copie de travail)
@@ -29,7 +29,7 @@
 const char *Py_FileSystemDefaultEncoding = NULL; /* set by initfsencoding() */
 int Py_HasFileSystemDefaultEncoding = 0;
 #else
-const char *Py_FileSystemDefaultEncoding = "utf-8";
+const char *Py_FileSystemDefaultEncoding = "ascii";
 int Py_HasFileSystemDefaultEncoding = 1;
 #endif
 
Index: Include/unicodeobject.h
===================================================================
--- Include/unicodeobject.h	(révision 81227)
+++ Include/unicodeobject.h	(copie de travail)
@@ -1248,7 +1248,7 @@
 /* Decode a null-terminated string using Py_FileSystemDefaultEncoding
    and the "surrogateescape" error handler.
 
-   If Py_FileSystemDefaultEncoding is not set, fall back to UTF-8.
+   If Py_FileSystemDefaultEncoding is not set, fall back to ASCII.
 
    Use PyUnicode_DecodeFSDefaultAndSize() if the string length is known.
 */
@@ -1260,7 +1260,7 @@
 /* Decode a string using Py_FileSystemDefaultEncoding
    and the "surrogateescape" error handler.
 
-   If Py_FileSystemDefaultEncoding is not set, fall back to UTF-8.
+   If Py_FileSystemDefaultEncoding is not set, fall back to ASCII.
 */
 
 PyAPI_FUNC(PyObject*) PyUnicode_DecodeFSDefaultAndSize(
@@ -1271,7 +1271,7 @@
 /* Encode a Unicode object to Py_FileSystemDefaultEncoding with the
    "surrogateescape" error handler, and return bytes.
 
-   If Py_FileSystemDefaultEncoding is not set, fall back to UTF-8.
+   If Py_FileSystemDefaultEncoding is not set, fall back to ASCII.
 */
 
 PyAPI_FUNC(PyObject*) PyUnicode_EncodeFSDefault(
Index: Objects/unicodeobject.c
===================================================================
--- Objects/unicodeobject.c	(révision 81227)
+++ Objects/unicodeobject.c	(copie de travail)
@@ -1468,7 +1468,7 @@
                                          Py_FileSystemDefaultEncoding,
                                          "surrogateescape");
     else
-        return PyUnicode_EncodeUTF8(PyUnicode_AS_UNICODE(unicode),
+        return PyUnicode_EncodeASCII(PyUnicode_AS_UNICODE(unicode),
                                      PyUnicode_GET_SIZE(unicode),
                                      "surrogateescape");
 }
@@ -1632,7 +1632,7 @@
                                 "surrogateescape");
     }
     else {
-        return PyUnicode_DecodeUTF8(s, size, "surrogateescape");
+        return PyUnicode_DecodeASCII(s, size, "surrogateescape");
     }
 }
 
Index: Doc/c-api/unicode.rst
===================================================================
--- Doc/c-api/unicode.rst	(révision 81227)
+++ Doc/c-api/unicode.rst	(copie de travail)
@@ -392,7 +392,7 @@
    Decode a null-terminated string using :cdata:`Py_FileSystemDefaultEncoding`
    and the ``"surrogateescape"`` error handler.
 
-   If :cdata:`Py_FileSystemDefaultEncoding` is not set, fall back to UTF-8.
+   If :cdata:`Py_FileSystemDefaultEncoding` is not set, fall back to ASCII.
 
    Use :func:`PyUnicode_DecodeFSDefaultAndSize` if you know the string length.
 
@@ -402,7 +402,7 @@
    Decode a string using :cdata:`Py_FileSystemDefaultEncoding` and
    the ``"surrogateescape"`` error handler.
 
-   If :cdata:`Py_FileSystemDefaultEncoding` is not set, fall back to UTF-8.
+   If :cdata:`Py_FileSystemDefaultEncoding` is not set, fall back to ASCII.
 
 
 .. cfunction:: PyObject* PyUnicode_EncodeFSDefault(PyObject *unicode)
@@ -410,7 +410,7 @@
    Encode a Unicode object to :cdata:`Py_FileSystemDefaultEncoding` with the
    ``'surrogateescape'`` error handler, and return :class:`bytes`.
 
-   If :cdata:`Py_FileSystemDefaultEncoding` is not set, fall back to UTF-8.
+   If :cdata:`Py_FileSystemDefaultEncoding` is not set, fall back to ASCII.
 
    .. versionadded:: 3.2
 
Index: Doc/library/sys.rst
===================================================================
--- Doc/library/sys.rst	(révision 81227)
+++ Doc/library/sys.rst	(copie de travail)
@@ -304,7 +304,7 @@
    * On Mac OS X, the encoding is ``'utf-8'``.
 
    * On Unix, the encoding is the user's preference according to the result of
-     nl_langinfo(CODESET), or ``'utf-8'`` if ``nl_langinfo(CODESET)`` failed.
+     nl_langinfo(CODESET), or ``'ascii'`` if ``nl_langinfo(CODESET)`` failed.
 
    * On Windows NT+, file names are Unicode natively, so no conversion is
      performed. :func:`getfilesystemencoding` still returns ``'mbcs'``, as