diff --git a/Include/cpython/coreconfig.h b/Include/cpython/coreconfig.h
index 1aab5e4..5672080 100644
--- a/Include/cpython/coreconfig.h
+++ b/Include/cpython/coreconfig.h
@@ -207,8 +207,8 @@
 
        See Py_FileSystemDefaultEncoding and Py_FileSystemDefaultEncodeErrors.
        */
-    char *filesystem_encoding;
-    char *filesystem_errors;
+    wchar_t *filesystem_encoding;
+    wchar_t *filesystem_errors;
 
     wchar_t *pycache_prefix;  /* PYTHONPYCACHEPREFIX, -X pycache_prefix=PATH */
     wchar_t *program_name;    /* Program name, see also Py_GetProgramName() */
@@ -334,13 +334,13 @@
        Value set from PYTHONIOENCODING environment variable and
        Py_SetStandardStreamEncoding() function.
        See also 'stdio_errors' attribute. */
-    char *stdio_encoding;
+    wchar_t *stdio_encoding;
 
     /* Error handler of sys.stdin and sys.stdout.
        Value set from PYTHONIOENCODING environment variable and
        Py_SetStandardStreamEncoding() function.
        See also 'stdio_encoding' attribute. */
-    char *stdio_errors;
+    wchar_t *stdio_errors;
 
 #ifdef MS_WINDOWS
     /* If greater than zero, use io.FileIO instead of WindowsConsoleIO for sys
diff --git a/Include/internal/pycore_coreconfig.h b/Include/internal/pycore_coreconfig.h
index 8af310d..d48904e 100644
--- a/Include/internal/pycore_coreconfig.h
+++ b/Include/internal/pycore_coreconfig.h
@@ -106,12 +106,9 @@
     _PyCoreConfig *config,
     const _PyCoreConfig *config2);
 PyAPI_FUNC(_PyInitError) _PyCoreConfig_SetString(
-    char **config_str,
-    const char *str);
-PyAPI_FUNC(_PyInitError) _PyCoreConfig_SetWideString(
     wchar_t **config_str,
     const wchar_t *str);
-PyAPI_FUNC(_PyInitError) _PyCoreConfig_SetWideStringFromString(
+PyAPI_FUNC(_PyInitError) _PyCoreConfig_DecodeLocale(
     wchar_t **config_str,
     const char *str);
 PyAPI_FUNC(_PyInitError) _PyCoreConfig_InitPathConfig(_PyCoreConfig *config);
diff --git a/Include/internal/pycore_pylifecycle.h b/Include/internal/pycore_pylifecycle.h
index a2383d4..321cc5d 100644
--- a/Include/internal/pycore_pylifecycle.h
+++ b/Include/internal/pycore_pylifecycle.h
@@ -21,6 +21,9 @@
     const char *errors);
 extern void _Py_ClearFileSystemEncoding(void);
 extern _PyInitError _PyUnicode_InitEncodings(PyInterpreterState *interp);
+#ifdef MS_WINDOWS
+extern int _PyUnicode_EnableLegacyWindowsFSEncoding(void);
+#endif
 
 PyAPI_FUNC(void) _Py_ClearStandardStreamEncoding(void);
 
diff --git a/Include/internal/pycore_pystate.h b/Include/internal/pycore_pystate.h
index 2c24f67..67bcd14 100644
--- a/Include/internal/pycore_pystate.h
+++ b/Include/internal/pycore_pystate.h
@@ -56,7 +56,14 @@
     PyObject *codec_search_cache;
     PyObject *codec_error_registry;
     int codecs_initialized;
-    int fscodec_initialized;
+
+    /* fs_codec.encoding is initialized to NULL.
+       Later, it is set to a non-NULL string by _PyUnicode_InitEncodings(). */
+    struct {
+        char *encoding;   /* Filesystem encoding (encoded to UTF-8) */
+        char *errors;     /* Filesystem errors (encoded to UTF-8) */
+        _Py_error_handler error_handler;
+    } fs_codec;
 
     _PyCoreConfig core_config;
 #ifdef HAVE_DLOPEN
diff --git a/Objects/stringlib/codecs.h b/Objects/stringlib/codecs.h
index 0abb4c8..8645bc2 100644
--- a/Objects/stringlib/codecs.h
+++ b/Objects/stringlib/codecs.h
@@ -260,6 +260,7 @@
 STRINGLIB(utf8_encoder)(PyObject *unicode,
                         STRINGLIB_CHAR *data,
                         Py_ssize_t size,
+                        _Py_error_handler error_handler,
                         const char *errors)
 {
     Py_ssize_t i;                /* index into data of next input character */
@@ -268,7 +269,6 @@
     PyObject *error_handler_obj = NULL;
     PyObject *exc = NULL;
     PyObject *rep = NULL;
-    _Py_error_handler error_handler = _Py_ERROR_UNKNOWN;
 #endif
 #if STRINGLIB_SIZEOF_CHAR == 1
     const Py_ssize_t max_char_size = 2;
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 5b6b241..4d86519e8 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -40,6 +40,7 @@
 
 #define PY_SSIZE_T_CLEAN
 #include "Python.h"
+#include "pycore_coreconfig.h"
 #include "pycore_fileutils.h"
 #include "pycore_object.h"
 #include "pycore_pylifecycle.h"
@@ -264,6 +265,13 @@
 /* Forward declaration */
 static inline int
 _PyUnicodeWriter_WriteCharInline(_PyUnicodeWriter *writer, Py_UCS4 ch);
+static PyObject *
+unicode_encode_utf8(PyObject *unicode, _Py_error_handler error_handler,
+                    const char *errors);
+static PyObject *
+unicode_decode_utf8(const char *s, Py_ssize_t size,
+                    _Py_error_handler error_handler, const char *errors,
+                    Py_ssize_t *consumed);
 
 /* List of static strings. */
 static _Py_Identifier *static_strings = NULL;
@@ -388,6 +396,35 @@
     return _Py_ERROR_OTHER;
 }
 
+
+static _Py_error_handler
+get_error_handler_wide(const wchar_t *errors)
+{
+    if (errors == NULL || wcscmp(errors, L"strict") == 0) {
+        return _Py_ERROR_STRICT;
+    }
+    if (wcscmp(errors, L"surrogateescape") == 0) {
+        return _Py_ERROR_SURROGATEESCAPE;
+    }
+    if (wcscmp(errors, L"replace") == 0) {
+        return _Py_ERROR_REPLACE;
+    }
+    if (wcscmp(errors, L"ignore") == 0) {
+        return _Py_ERROR_IGNORE;
+    }
+    if (wcscmp(errors, L"backslashreplace") == 0) {
+        return _Py_ERROR_BACKSLASHREPLACE;
+    }
+    if (wcscmp(errors, L"surrogatepass") == 0) {
+        return _Py_ERROR_SURROGATEPASS;
+    }
+    if (wcscmp(errors, L"xmlcharrefreplace") == 0) {
+        return _Py_ERROR_XMLCHARREFREPLACE;
+    }
+    return _Py_ERROR_OTHER;
+}
+
+
 /* The max unicode value is always 0x10FFFF while using the PEP-393 API.
    This function is kept for backward compatibility with the old API. */
 Py_UNICODE
@@ -3445,11 +3482,9 @@
 
 
 static PyObject *
-unicode_encode_locale(PyObject *unicode, const char *errors,
+unicode_encode_locale(PyObject *unicode, _Py_error_handler error_handler,
                       int current_locale)
 {
-    _Py_error_handler error_handler = _Py_GetErrorHandler(errors);
-
     Py_ssize_t wlen;
     wchar_t *wstr = PyUnicode_AsWideCharString(unicode, &wlen);
     if (wstr == NULL) {
@@ -3499,30 +3534,44 @@
 PyObject *
 PyUnicode_EncodeLocale(PyObject *unicode, const char *errors)
 {
-    return unicode_encode_locale(unicode, errors, 1);
+    _Py_error_handler error_handler = _Py_GetErrorHandler(errors);
+    return unicode_encode_locale(unicode, error_handler, 1);
 }
 
 PyObject *
 PyUnicode_EncodeFSDefault(PyObject *unicode)
 {
     PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
-    const _PyCoreConfig *config = &interp->core_config;
 #ifdef _Py_FORCE_UTF8_FS_ENCODING
-    return _PyUnicode_AsUTF8String(unicode, config->filesystem_errors);
+    if (interp->fs_codec.encoding) {
+        return unicode_encode_utf8(unicode,
+                                   interp->fs_codec.error_handler,
+                                   interp->fs_codec.errors);
+    }
+    else {
+        const _PyCoreConfig *config = &interp->core_config;
+        _Py_error_handler errors;
+        errors = get_error_handler_wide(config->filesystem_errors);
+        assert(errors != _Py_ERROR_UNKNOWN);
+        return unicode_encode_utf8(unicode, errors, NULL);
+    }
 #else
     /* Bootstrap check: if the filesystem codec is implemented in Python, we
        cannot use it to encode and decode filenames before it is loaded. Load
        the Python codec requires to encode at least its own filename. Use the C
        implementation of the locale codec until the codec registry is
        initialized and the Python codec is loaded. See initfsencoding(). */
-    if (interp->fscodec_initialized) {
+    if (interp->fs_codec.encoding) {
         return PyUnicode_AsEncodedString(unicode,
-                                         config->filesystem_encoding,
-                                         config->filesystem_errors);
+                                         interp->fs_codec.encoding,
+                                         interp->fs_codec.errors);
     }
     else {
-        return unicode_encode_locale(unicode,
-                                     config->filesystem_errors, 0);
+        const _PyCoreConfig *config = &interp->core_config;
+        _Py_error_handler errors;
+        errors = get_error_handler_wide(config->filesystem_errors);
+        assert(errors != _Py_ERROR_UNKNOWN);
+        return unicode_encode_locale(unicode, errors, 0);
     }
 #endif
 }
@@ -3663,11 +3712,9 @@
 }
 
 static PyObject*
-unicode_decode_locale(const char *str, Py_ssize_t len, const char *errors,
-                      int current_locale)
+unicode_decode_locale(const char *str, Py_ssize_t len,
+                      _Py_error_handler errors, int current_locale)
 {
-    _Py_error_handler error_handler = _Py_GetErrorHandler(errors);
-
     if (str[len] != '\0' || (size_t)len != strlen(str))  {
         PyErr_SetString(PyExc_ValueError, "embedded null byte");
         return NULL;
@@ -3677,7 +3724,7 @@
     size_t wlen;
     const char *reason;
     int res = _Py_DecodeLocaleEx(str, &wstr, &wlen, &reason,
-                                 current_locale, error_handler);
+                                 current_locale, errors);
     if (res != 0) {
         if (res == -2) {
             PyObject *exc;
@@ -3709,14 +3756,16 @@
 PyUnicode_DecodeLocaleAndSize(const char *str, Py_ssize_t len,
                               const char *errors)
 {
-    return unicode_decode_locale(str, len, errors, 1);
+    _Py_error_handler error_handler = _Py_GetErrorHandler(errors);
+    return unicode_decode_locale(str, len, error_handler, 1);
 }
 
 PyObject*
 PyUnicode_DecodeLocale(const char *str, const char *errors)
 {
     Py_ssize_t size = (Py_ssize_t)strlen(str);
-    return unicode_decode_locale(str, size, errors, 1);
+    _Py_error_handler error_handler = _Py_GetErrorHandler(errors);
+    return unicode_decode_locale(str, size, error_handler, 1);
 }
 
 
@@ -3730,23 +3779,36 @@
 PyUnicode_DecodeFSDefaultAndSize(const char *s, Py_ssize_t size)
 {
     PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
-    const _PyCoreConfig *config = &interp->core_config;
 #ifdef _Py_FORCE_UTF8_FS_ENCODING
-    return PyUnicode_DecodeUTF8Stateful(s, size, config->filesystem_errors, NULL);
+    if (interp->fs_codec.encoding) {
+        return unicode_decode_utf8(s, size,
+                                   interp->fs_codec.error_handler,
+                                   interp->fs_codec.errors,
+                                   NULL);
+    }
+    else {
+        const _PyCoreConfig *config = &interp->core_config;
+        _Py_error_handler errors;
+        errors = get_error_handler_wide(config->filesystem_errors);
+        assert(errors != _Py_ERROR_UNKNOWN);
+        return unicode_decode_utf8(s, size, errors, NULL, NULL);
+    }
 #else
     /* Bootstrap check: if the filesystem codec is implemented in Python, we
        cannot use it to encode and decode filenames before it is loaded. Load
        the Python codec requires to encode at least its own filename. Use the C
        implementation of the locale codec until the codec registry is
        initialized and the Python codec is loaded. See initfsencoding(). */
-    if (interp->fscodec_initialized) {
+    if (interp->fs_codec.encoding) {
         return PyUnicode_Decode(s, size,
-                                config->filesystem_encoding,
-                                config->filesystem_errors);
+                                interp->fs_codec.encoding,
+                                interp->fs_codec.errors);
     }
     else {
-        return unicode_decode_locale(s, size,
-                                     config->filesystem_errors, 0);
+        const _PyCoreConfig *config = &interp->core_config;
+        _Py_error_handler errors;
+        errors = get_error_handler_wide(config->filesystem_errors);
+        return unicode_decode_locale(s, size, errors, 0);
     }
 #endif
 }
@@ -4810,11 +4872,10 @@
     return p - start;
 }
 
-PyObject *
-PyUnicode_DecodeUTF8Stateful(const char *s,
-                             Py_ssize_t size,
-                             const char *errors,
-                             Py_ssize_t *consumed)
+static PyObject *
+unicode_decode_utf8(const char *s, Py_ssize_t size,
+                    _Py_error_handler error_handler, const char *errors,
+                    Py_ssize_t *consumed)
 {
     _PyUnicodeWriter writer;
     const char *starts = s;
@@ -4825,7 +4886,6 @@
     const char *errmsg = "";
     PyObject *error_handler_obj = NULL;
     PyObject *exc = NULL;
-    _Py_error_handler error_handler = _Py_ERROR_UNKNOWN;
 
     if (size == 0) {
         if (consumed)
@@ -4948,6 +5008,16 @@
 }
 
 
+PyObject *
+PyUnicode_DecodeUTF8Stateful(const char *s,
+                             Py_ssize_t size,
+                             const char *errors,
+                             Py_ssize_t *consumed)
+{
+    return unicode_decode_utf8(s, size, _Py_ERROR_UNKNOWN, errors, consumed);
+}
+
+
 /* UTF-8 decoder: use surrogateescape error handler if 'surrogateescape' is
    non-zero, use strict error handler otherwise.
 
@@ -5231,8 +5301,9 @@
    maximum possible needed (4 result bytes per Unicode character), and return
    the excess memory at the end.
 */
-PyObject *
-_PyUnicode_AsUTF8String(PyObject *unicode, const char *errors)
+static PyObject *
+unicode_encode_utf8(PyObject *unicode, _Py_error_handler error_handler,
+                    const char *errors)
 {
     enum PyUnicode_Kind kind;
     void *data;
@@ -5260,15 +5331,22 @@
     case PyUnicode_1BYTE_KIND:
         /* the string cannot be ASCII, or PyUnicode_UTF8() would be set */
         assert(!PyUnicode_IS_ASCII(unicode));
-        return ucs1lib_utf8_encoder(unicode, data, size, errors);
+        return ucs1lib_utf8_encoder(unicode, data, size, error_handler, errors);
     case PyUnicode_2BYTE_KIND:
-        return ucs2lib_utf8_encoder(unicode, data, size, errors);
+        return ucs2lib_utf8_encoder(unicode, data, size, error_handler, errors);
     case PyUnicode_4BYTE_KIND:
-        return ucs4lib_utf8_encoder(unicode, data, size, errors);
+        return ucs4lib_utf8_encoder(unicode, data, size, error_handler, errors);
     }
 }
 
 PyObject *
+_PyUnicode_AsUTF8String(PyObject *unicode, const char *errors)
+{
+    return unicode_encode_utf8(unicode, _Py_ERROR_UNKNOWN, errors);
+}
+
+
+PyObject *
 PyUnicode_EncodeUTF8(const Py_UNICODE *s,
                      Py_ssize_t size,
                      const char *errors)
@@ -15575,12 +15653,35 @@
 }
 
 
-static char*
-get_codec_name(const char *encoding)
+static int
+encode_wstr_utf8(wchar_t *wstr, char **str, const char *name)
 {
-    PyObject *codec, *name_obj = NULL;
+    int res;
+    res = _Py_EncodeUTF8Ex(wstr, str, NULL, NULL, 1, _Py_ERROR_STRICT);
+    if (res == -2) {
+        PyErr_Format(PyExc_RuntimeWarning, "cannot decode %s", name);
+        return -1;
+    }
+    if (res < 0) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    return 0;
+}
 
-    codec = _PyCodec_Lookup(encoding);
+
+static int
+config_get_codec_name(wchar_t **config_encoding)
+{
+    char *encoding;
+    if (encode_wstr_utf8(*config_encoding, &encoding, "stdio_encoding") < 0) {
+        return -1;
+    }
+
+    PyObject *name_obj = NULL;
+    PyObject *codec = _PyCodec_Lookup(encoding);
+    PyMem_RawFree(encoding);
+
     if (!codec)
         goto error;
 
@@ -15590,71 +15691,107 @@
         goto error;
     }
 
-    const char *name_utf8 = PyUnicode_AsUTF8(name_obj);
-    if (name_utf8 == NULL) {
+    wchar_t *wname = PyUnicode_AsWideCharString(name_obj, NULL);
+    Py_DECREF(name_obj);
+    if (wname == NULL) {
         goto error;
     }
 
-    char *name = _PyMem_RawStrdup(name_utf8);
-    Py_DECREF(name_obj);
-    if (name == NULL) {
+    wchar_t *raw_wname = _PyMem_RawWcsdup(wname);
+    if (raw_wname == NULL) {
+        PyMem_Free(wname);
         PyErr_NoMemory();
-        return NULL;
+        goto error;
     }
-    return name;
+
+    PyMem_RawFree(*config_encoding);
+    *config_encoding = raw_wname;
+
+    PyMem_Free(wname);
+    return 0;
 
 error:
     Py_XDECREF(codec);
     Py_XDECREF(name_obj);
-    return NULL;
+    return -1;
 }
 
 
 static _PyInitError
 init_stdio_encoding(PyInterpreterState *interp)
 {
+    /* Update the stdio encoding to the normalized Python codec name. */
     _PyCoreConfig *config = &interp->core_config;
-
-    char *codec_name = get_codec_name(config->stdio_encoding);
-    if (codec_name == NULL) {
+    if (config_get_codec_name(&config->stdio_encoding) < 0) {
         return _Py_INIT_ERR("failed to get the Python codec name "
                             "of the stdio encoding");
     }
-    PyMem_RawFree(config->stdio_encoding);
-    config->stdio_encoding = codec_name;
     return _Py_INIT_OK();
 }
 
 
+static int
+init_fs_codec(PyInterpreterState *interp)
+{
+    _PyCoreConfig *config = &interp->core_config;
+
+    _Py_error_handler error_handler;
+    error_handler = get_error_handler_wide(config->filesystem_errors);
+    if (error_handler == _Py_ERROR_UNKNOWN) {
+        PyErr_SetString(PyExc_RuntimeError, "unknow filesystem error handler");
+        return -1;
+    }
+
+    char *encoding, *errors;
+    if (encode_wstr_utf8(config->filesystem_encoding,
+                         &encoding,
+                         "filesystem_encoding") < 0) {
+        return -1;
+    }
+
+    if (encode_wstr_utf8(config->filesystem_errors,
+                         &errors,
+                         "filesystem_errors") < 0) {
+        PyMem_RawFree(encoding);
+        return -1;
+    }
+
+    PyMem_RawFree(interp->fs_codec.encoding);
+    interp->fs_codec.encoding = encoding;
+    PyMem_RawFree(interp->fs_codec.errors);
+    interp->fs_codec.errors = errors;
+    interp->fs_codec.error_handler = error_handler;
+
+    /* At this point, PyUnicode_EncodeFSDefault() and
+       PyUnicode_DecodeFSDefault() can now use the Python codec rather than
+       the C implementation of the filesystem encoding. */
+
+    /* Set Py_FileSystemDefaultEncoding and Py_FileSystemDefaultEncodeErrors
+       global configuration variables. */
+    if (_Py_SetFileSystemEncoding(interp->fs_codec.encoding,
+                                  interp->fs_codec.errors) < 0) {
+        PyErr_NoMemory();
+        return -1;
+    }
+    return 0;
+}
+
+
 static _PyInitError
 init_fs_encoding(PyInterpreterState *interp)
 {
+    /* Update the filesystem encoding to the normalized Python codec name.
+       For example, replace "ANSI_X3.4-1968" (locale encoding) with "ascii"
+       (Python codec name). */
     _PyCoreConfig *config = &interp->core_config;
-
-    char *encoding = get_codec_name(config->filesystem_encoding);
-    if (encoding == NULL) {
-        /* Such error can only occurs in critical situations: no more
-           memory, import a module of the standard library failed, etc. */
+    if (config_get_codec_name(&config->filesystem_encoding) < 0) {
         return _Py_INIT_ERR("failed to get the Python codec "
                             "of the filesystem encoding");
     }
 
-    /* Update the filesystem encoding to the normalized Python codec name.
-       For example, replace "ANSI_X3.4-1968" (locale encoding) with "ascii"
-       (Python codec name). */
-    PyMem_RawFree(config->filesystem_encoding);
-    config->filesystem_encoding = encoding;
-
-    /* Set Py_FileSystemDefaultEncoding and Py_FileSystemDefaultEncodeErrors
-       global configuration variables. */
-    if (_Py_SetFileSystemEncoding(config->filesystem_encoding,
-                                  config->filesystem_errors) < 0) {
-        return _Py_INIT_NO_MEMORY();
+    if (init_fs_codec(interp) < 0) {
+        return _Py_INIT_ERR("cannot initialize filesystem codec");
     }
-
-    /* PyUnicode can now use the Python codec rather than C implementation
-       for the filesystem encoding */
-    interp->fscodec_initialized = 1;
     return _Py_INIT_OK();
 }
 
@@ -15671,6 +15808,33 @@
 }
 
 
+#ifdef MS_WINDOWS
+int
+_PyUnicode_EnableLegacyWindowsFSEncoding(void)
+{
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
+    _PyCoreConfig *config = &interp->core_config;
+
+    /* Set the filesystem encoding to mbcs/replace (PEP 529) */
+    wchar_t *encoding = _PyMem_RawWcsdup(L"mbcs");
+    wchar_t *errors = _PyMem_RawWcsdup(L"replace");
+    if (encoding == NULL || errors == NULL) {
+        PyMem_RawFree(encoding);
+        PyMem_RawFree(errors);
+        PyErr_NoMemory();
+        return -1;
+    }
+
+    PyMem_RawFree(config->filesystem_encoding);
+    config->filesystem_encoding = encoding;
+    PyMem_RawFree(config->filesystem_errors);
+    config->filesystem_errors = errors;
+
+    return init_fs_codec(interp);
+}
+#endif
+
+
 void
 _PyUnicode_Fini(void)
 {
@@ -15694,6 +15858,12 @@
     }
     _PyUnicode_ClearStaticStrings();
     (void)PyUnicode_ClearFreeList();
+
+    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
+    PyMem_RawFree(interp->fs_codec.encoding);
+    interp->fs_codec.encoding = NULL;
+    PyMem_RawFree(interp->fs_codec.errors);
+    interp->fs_codec.errors = NULL;
 }
 
 
diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index 6e764e3..2cadf82 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -488,8 +488,8 @@
        Force it to 0 through the config. */
     config.legacy_windows_stdio = 0;
 #endif
-    config.stdio_encoding = "iso8859-1";
-    config.stdio_errors = "replace";
+    config.stdio_encoding = L"iso8859-1";
+    config.stdio_errors = L"replace";
 
     putenv("PYTHONNOUSERSITE=");
     Py_NoUserSiteDirectory = 0;
diff --git a/Python/coreconfig.c b/Python/coreconfig.c
index c40c1f8..15643be 100644
--- a/Python/coreconfig.c
+++ b/Python/coreconfig.c
@@ -523,27 +523,7 @@
 
 /* Copy str into *config_str (duplicate the string) */
 _PyInitError
-_PyCoreConfig_SetString(char **config_str, const char *str)
-{
-    char *str2;
-    if (str != NULL) {
-        str2 = _PyMem_RawStrdup(str);
-        if (str2 == NULL) {
-            return _Py_INIT_NO_MEMORY();
-        }
-    }
-    else {
-        str2 = NULL;
-    }
-    PyMem_RawFree(*config_str);
-    *config_str = str2;
-    return _Py_INIT_OK();
-}
-
-
-/* Copy str into *config_str (duplicate the string) */
-_PyInitError
-_PyCoreConfig_SetWideString(wchar_t **config_str, const wchar_t *str)
+_PyCoreConfig_SetString(wchar_t **config_str, const wchar_t *str)
 {
     wchar_t *str2;
     if (str != NULL) {
@@ -563,8 +543,8 @@
 
 /* Decode str using Py_DecodeLocale() and set the result into *config_str */
 static _PyInitError
-_PyCoreConfig_SetWideStringFromStringErr(wchar_t **config_str, const char *str,
-                                         const char *decode_err_msg)
+_PyCoreConfig_DecodeLocaleErr(wchar_t **config_str, const char *str,
+                              const char *decode_err_msg)
 {
     wchar_t *str2;
     if (str != NULL) {
@@ -588,17 +568,15 @@
 }
 
 
-_PyInitError
-_PyCoreConfig_SetWideStringFromString(wchar_t **config_str, const char *str)
-{
-    return _PyCoreConfig_SetWideStringFromStringErr(
-                config_str, str, "cannot decode string");
-}
-
-
 #define CONFIG_DECODE_LOCALE(config_str, str, NAME) \
-    _PyCoreConfig_SetWideStringFromStringErr(config_str, str, \
-                                             "cannot decode " NAME)
+    _PyCoreConfig_DecodeLocaleErr(config_str, str, "cannot decode " NAME)
+
+
+_PyInitError
+_PyCoreConfig_DecodeLocale(wchar_t **config_str, const char *str)
+{
+    return CONFIG_DECODE_LOCALE(config_str, str, "string");
+}
 
 
 _PyInitError
@@ -608,16 +586,9 @@
     _PyCoreConfig_Clear(config);
 
 #define COPY_ATTR(ATTR) config->ATTR = config2->ATTR
-#define COPY_STR_ATTR(ATTR) \
-    do { \
-        err = _PyCoreConfig_SetString(&config->ATTR, config2->ATTR); \
-        if (_Py_INIT_FAILED(err)) { \
-            return err; \
-        } \
-    } while (0)
 #define COPY_WSTR_ATTR(ATTR) \
     do { \
-        err = _PyCoreConfig_SetWideString(&config->ATTR, config2->ATTR); \
+        err = _PyCoreConfig_SetString(&config->ATTR, config2->ATTR); \
         if (_Py_INIT_FAILED(err)) { \
             return err; \
         } \
@@ -676,10 +647,10 @@
     COPY_ATTR(quiet);
     COPY_ATTR(user_site_directory);
     COPY_ATTR(buffered_stdio);
-    COPY_STR_ATTR(filesystem_encoding);
-    COPY_STR_ATTR(filesystem_errors);
-    COPY_STR_ATTR(stdio_encoding);
-    COPY_STR_ATTR(stdio_errors);
+    COPY_WSTR_ATTR(filesystem_encoding);
+    COPY_WSTR_ATTR(filesystem_errors);
+    COPY_WSTR_ATTR(stdio_encoding);
+    COPY_WSTR_ATTR(stdio_errors);
 #ifdef MS_WINDOWS
     COPY_ATTR(legacy_windows_stdio);
 #endif
@@ -692,7 +663,6 @@
     COPY_ATTR(_init_main);
 
 #undef COPY_ATTR
-#undef COPY_STR_ATTR
 #undef COPY_WSTR_ATTR
 #undef COPY_WSTRLIST
     return _Py_INIT_OK();
@@ -721,16 +691,10 @@
                 goto fail; \
             } \
         } while (0)
-#define FROM_STRING(STR) \
-    ((STR != NULL) ? \
-        PyUnicode_FromString(STR) \
-        : (Py_INCREF(Py_None), Py_None))
 #define SET_ITEM_INT(ATTR) \
     SET_ITEM(#ATTR, PyLong_FromLong(config->ATTR))
 #define SET_ITEM_UINT(ATTR) \
     SET_ITEM(#ATTR, PyLong_FromUnsignedLong(config->ATTR))
-#define SET_ITEM_STR(ATTR) \
-    SET_ITEM(#ATTR, FROM_STRING(config->ATTR))
 #define FROM_WSTRING(STR) \
     ((STR != NULL) ? \
         PyUnicode_FromWideChar(STR, -1) \
@@ -753,8 +717,8 @@
     SET_ITEM_INT(show_alloc_count);
     SET_ITEM_INT(dump_refs);
     SET_ITEM_INT(malloc_stats);
-    SET_ITEM_STR(filesystem_encoding);
-    SET_ITEM_STR(filesystem_errors);
+    SET_ITEM_WSTR(filesystem_encoding);
+    SET_ITEM_WSTR(filesystem_errors);
     SET_ITEM_WSTR(pycache_prefix);
     SET_ITEM_WSTR(program_name);
     SET_ITEM_WSTRLIST(argv);
@@ -783,8 +747,8 @@
     SET_ITEM_INT(quiet);
     SET_ITEM_INT(user_site_directory);
     SET_ITEM_INT(buffered_stdio);
-    SET_ITEM_STR(stdio_encoding);
-    SET_ITEM_STR(stdio_errors);
+    SET_ITEM_WSTR(stdio_encoding);
+    SET_ITEM_WSTR(stdio_errors);
 #ifdef MS_WINDOWS
     SET_ITEM_INT(legacy_windows_stdio);
 #endif
@@ -803,12 +767,10 @@
     Py_DECREF(dict);
     return NULL;
 
-#undef FROM_STRING
 #undef FROM_WSTRING
 #undef SET_ITEM
 #undef SET_ITEM_INT
 #undef SET_ITEM_UINT
-#undef SET_ITEM_STR
 #undef SET_ITEM_WSTR
 #undef SET_ITEM_WSTRLIST
 }
@@ -845,7 +807,7 @@
         return _Py_INIT_OK();
     }
 
-    return _PyCoreConfig_SetWideString(dest, var);
+    return _PyCoreConfig_SetString(dest, var);
 #else
     const char *var = getenv(name);
     if (!var || var[0] == '\0') {
@@ -853,7 +815,7 @@
         return _Py_INIT_OK();
     }
 
-    return _PyCoreConfig_SetWideStringFromStringErr(dest, var, decode_err_msg);
+    return _PyCoreConfig_DecodeLocaleErr(dest, var, decode_err_msg);
 #endif
 }
 
@@ -996,8 +958,7 @@
 
     /* Use argv[0] by default, if available */
     if (config->program != NULL) {
-        err = _PyCoreConfig_SetWideString(&config->program_name,
-                                          config->program);
+        err = _PyCoreConfig_SetString(&config->program_name, config->program);
         if (_Py_INIT_FAILED(err)) {
             return err;
         }
@@ -1010,7 +971,7 @@
 #else
     const wchar_t *default_program_name = L"python3";
 #endif
-    err = _PyCoreConfig_SetWideString(&config->program_name, default_program_name);
+    err = _PyCoreConfig_SetString(&config->program_name, default_program_name);
     if (_Py_INIT_FAILED(err)) {
         return err;
     }
@@ -1025,8 +986,8 @@
     /* If Py_SetProgramFullPath() was called, use its value */
     const wchar_t *program_full_path = _Py_path_config.program_full_path;
     if (program_full_path != NULL) {
-        _PyInitError err = _PyCoreConfig_SetWideString(&config->executable,
-                                                       program_full_path);
+        _PyInitError err = _PyCoreConfig_SetString(&config->executable,
+                                                   program_full_path);
         if (_Py_INIT_FAILED(err)) {
             return err;
         }
@@ -1051,7 +1012,7 @@
     /* If Py_SetPythonHome() was called, use its value */
     wchar_t *home = _Py_path_config.home;
     if (home) {
-        _PyInitError err = _PyCoreConfig_SetWideString(&config->home, home);
+        _PyInitError err = _PyCoreConfig_SetString(&config->home, home);
         if (_Py_INIT_FAILED(err)) {
             return err;
         }
@@ -1280,7 +1241,7 @@
 }
 
 
-static const char *
+static const wchar_t *
 config_get_stdio_errors(const _PyCoreConfig *config)
 {
 #ifndef MS_WINDOWS
@@ -1288,43 +1249,44 @@
     if (loc != NULL) {
         /* surrogateescape is the default in the legacy C and POSIX locales */
         if (strcmp(loc, "C") == 0 || strcmp(loc, "POSIX") == 0) {
-            return "surrogateescape";
+            return L"surrogateescape";
         }
 
 #ifdef PY_COERCE_C_LOCALE
         /* surrogateescape is the default in locale coercion target locales */
         if (_Py_IsLocaleCoercionTarget(loc)) {
-            return "surrogateescape";
+            return L"surrogateescape";
         }
 #endif
     }
 
-    return "strict";
+    return L"strict";
 #else
     /* On Windows, always use surrogateescape by default */
-    return "surrogateescape";
+    return L"surrogateescape";
 #endif
 }
 
 
 static _PyInitError
-config_get_locale_encoding(char **locale_encoding)
+config_get_locale_encoding(wchar_t **locale_encoding)
 {
 #ifdef MS_WINDOWS
     char encoding[20];
     PyOS_snprintf(encoding, sizeof(encoding), "cp%u", GetACP());
+    return _PyCoreConfig_DecodeLocale(locale_encoding, encoding);
 #elif defined(_Py_FORCE_UTF8_LOCALE)
-    const char *encoding = "UTF-8";
+    return _PyCoreConfig_SetString(locale_encoding, L"utf-8");
 #else
     const char *encoding = nl_langinfo(CODESET);
     if (!encoding || encoding[0] == '\0') {
         return _Py_INIT_ERR("failed to get the locale encoding: "
                             "nl_langinfo(CODESET) failed");
     }
+    /* nl_langinfo(CODESET) is decoded by Py_DecodeLocale() */
+    return CONFIG_DECODE_LOCALE(locale_encoding, encoding,
+                                "nl_langinfo(CODESET)");
 #endif
-
-    assert(*locale_encoding == NULL);
-    return _PyCoreConfig_SetString(locale_encoding, encoding);
 }
 
 
@@ -1337,16 +1299,18 @@
     /* If Py_SetStandardStreamEncoding() have been called, use these
         parameters. */
     if (config->stdio_encoding == NULL && _Py_StandardStreamEncoding != NULL) {
-        err = _PyCoreConfig_SetString(&config->stdio_encoding,
-                                      _Py_StandardStreamEncoding);
+        err = CONFIG_DECODE_LOCALE(&config->stdio_encoding,
+                                   _Py_StandardStreamEncoding,
+                                   "_Py_StandardStreamEncoding");
         if (_Py_INIT_FAILED(err)) {
             return err;
         }
     }
 
     if (config->stdio_errors == NULL && _Py_StandardStreamErrors != NULL) {
-        err = _PyCoreConfig_SetString(&config->stdio_errors,
-                                      _Py_StandardStreamErrors);
+        err = CONFIG_DECODE_LOCALE(&config->stdio_errors,
+                                   _Py_StandardStreamErrors,
+                                   "_Py_StandardStreamErrors");
         if (_Py_INIT_FAILED(err)) {
             return err;
         }
@@ -1359,11 +1323,9 @@
     /* PYTHONIOENCODING environment variable */
     const char *opt = _PyCoreConfig_GetEnv(config, "PYTHONIOENCODING");
     if (opt) {
-        /* _PyCoreConfig_SetString() requires dest to be initialized to NULL */
-        char *pythonioencoding = NULL;
-        err = _PyCoreConfig_SetString(&pythonioencoding, opt);
-        if (_Py_INIT_FAILED(err)) {
-            return err;
+        char *pythonioencoding = _PyMem_RawStrdup(opt);
+        if (pythonioencoding == NULL) {
+            return _Py_INIT_NO_MEMORY();
         }
 
         char *errors = strchr(pythonioencoding, ':');
@@ -1378,8 +1340,9 @@
         /* Does PYTHONIOENCODING contain an encoding? */
         if (pythonioencoding[0]) {
             if (config->stdio_encoding == NULL) {
-                err = _PyCoreConfig_SetString(&config->stdio_encoding,
-                                              pythonioencoding);
+                err = CONFIG_DECODE_LOCALE(&config->stdio_encoding,
+                                           pythonioencoding,
+                                           "PYTHONIOENCODING environment variable");
                 if (_Py_INIT_FAILED(err)) {
                     PyMem_RawFree(pythonioencoding);
                     return err;
@@ -1396,7 +1359,9 @@
         }
 
         if (config->stdio_errors == NULL && errors != NULL) {
-            err = _PyCoreConfig_SetString(&config->stdio_errors, errors);
+            err = CONFIG_DECODE_LOCALE(&config->stdio_errors,
+                                       errors,
+                                       "PYTHONIOENCODING environment variable");
             if (_Py_INIT_FAILED(err)) {
                 PyMem_RawFree(pythonioencoding);
                 return err;
@@ -1409,15 +1374,14 @@
     /* UTF-8 Mode uses UTF-8/surrogateescape */
     if (preconfig->utf8_mode) {
         if (config->stdio_encoding == NULL) {
-            err = _PyCoreConfig_SetString(&config->stdio_encoding,
-                                          "utf-8");
+            err = _PyCoreConfig_SetString(&config->stdio_encoding, L"utf-8");
             if (_Py_INIT_FAILED(err)) {
                 return err;
             }
         }
         if (config->stdio_errors == NULL) {
             err = _PyCoreConfig_SetString(&config->stdio_errors,
-                                          "surrogateescape");
+                                          L"surrogateescape");
             if (_Py_INIT_FAILED(err)) {
                 return err;
             }
@@ -1432,7 +1396,7 @@
         }
     }
     if (config->stdio_errors == NULL) {
-        const char *errors = config_get_stdio_errors(config);
+        const wchar_t *errors = config_get_stdio_errors(config);
         assert(errors != NULL);
 
         err = _PyCoreConfig_SetString(&config->stdio_errors, errors);
@@ -1452,33 +1416,32 @@
 
     if (config->filesystem_encoding == NULL) {
 #ifdef _Py_FORCE_UTF8_FS_ENCODING
-        err = _PyCoreConfig_SetString(&config->filesystem_encoding,
-                                      "utf-8");
+        err = _PyCoreConfig_SetString(&config->filesystem_encoding, L"utf-8");
 #else
 
 #ifdef MS_WINDOWS
         if (preconfig->legacy_windows_fs_encoding) {
             /* Legacy Windows filesystem encoding: mbcs/replace */
             err = _PyCoreConfig_SetString(&config->filesystem_encoding,
-                                          "mbcs");
+                                          L"mbcs");
         }
         else
 #endif
         if (preconfig->utf8_mode) {
             err = _PyCoreConfig_SetString(&config->filesystem_encoding,
-                                          "utf-8");
+                                          L"utf-8");
         }
 #ifndef MS_WINDOWS
         else if (_Py_GetForceASCII()) {
             err = _PyCoreConfig_SetString(&config->filesystem_encoding,
-                                          "ascii");
+                                          L"ascii");
         }
 #endif
         else {
 #ifdef MS_WINDOWS
             /* Windows defaults to utf-8/surrogatepass (PEP 529). */
             err = _PyCoreConfig_SetString(&config->filesystem_encoding,
-                                          "utf-8");
+                                          L"utf-8");
 #else
             err = config_get_locale_encoding(&config->filesystem_encoding);
 #endif
@@ -1491,16 +1454,16 @@
     }
 
     if (config->filesystem_errors == NULL) {
-        const char *errors;
+        const wchar_t *errors;
 #ifdef MS_WINDOWS
         if (preconfig->legacy_windows_fs_encoding) {
-            errors = "replace";
+            errors = L"replace";
         }
         else {
-            errors = "surrogatepass";
+            errors = L"surrogatepass";
         }
 #else
-        errors = "surrogateescape";
+        errors = L"surrogateescape";
 #endif
         err = _PyCoreConfig_SetString(&config->filesystem_errors, errors);
         if (_Py_INIT_FAILED(err)) {
@@ -1745,8 +1708,8 @@
                 || wcscmp(_PyOS_optarg, L"never") == 0
                 || wcscmp(_PyOS_optarg, L"default") == 0)
             {
-                err = _PyCoreConfig_SetWideString(&config->check_hash_pycs_mode,
-                                                  _PyOS_optarg);
+                err = _PyCoreConfig_SetString(&config->check_hash_pycs_mode,
+                                              _PyOS_optarg);
                 if (_Py_INIT_FAILED(err)) {
                     return err;
                 }
@@ -2119,7 +2082,7 @@
     }
 
     if (config->check_hash_pycs_mode == NULL) {
-        err = _PyCoreConfig_SetWideString(&config->check_hash_pycs_mode, L"default");
+        err = _PyCoreConfig_SetString(&config->check_hash_pycs_mode, L"default");
         if (_Py_INIT_FAILED(err)) {
             goto done;
         }
diff --git a/Python/preconfig.c b/Python/preconfig.c
index 108cbc6..48b9e83 100644
--- a/Python/preconfig.c
+++ b/Python/preconfig.c
@@ -14,7 +14,10 @@
 /* --- File system encoding/errors -------------------------------- */
 
 /* The filesystem encoding is chosen by config_init_fs_encoding(),
-   see also initfsencoding(). */
+   see also initfsencoding().
+
+   Py_FileSystemDefaultEncoding and Py_FileSystemDefaultEncodeErrors
+   are encoded to UTF-8. */
 const char *Py_FileSystemDefaultEncoding = NULL;
 int Py_HasFileSystemDefaultEncoding = 0;
 const char *Py_FileSystemDefaultEncodeErrors = NULL;
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index 01ef027..2a633cf 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -1668,7 +1668,7 @@
 static PyObject*
 create_stdio(const _PyCoreConfig *config, PyObject* io,
     int fd, int write_mode, const char* name,
-    const char* encoding, const char* errors)
+    const wchar_t* encoding, const wchar_t* errors)
 {
     PyObject *buf = NULL, *stream = NULL, *text = NULL, *raw = NULL, *res;
     const char* mode;
@@ -1718,7 +1718,7 @@
 #ifdef MS_WINDOWS
     /* Windows console IO is always UTF-8 encoded */
     if (PyWindowsConsoleIO_Check(raw))
-        encoding = "utf-8";
+        encoding = L"utf-8";
 #endif
 
     text = PyUnicode_FromString(name);
@@ -1754,10 +1754,25 @@
     newline = "\n";
 #endif
 
-    stream = _PyObject_CallMethodId(io, &PyId_TextIOWrapper, "OsssOO",
-                                    buf, encoding, errors,
+    PyObject *encoding_str = PyUnicode_FromWideChar(encoding, -1);
+    if (encoding_str == NULL) {
+        Py_CLEAR(buf);
+        goto error;
+    }
+
+    PyObject *errors_str = PyUnicode_FromWideChar(errors, -1);
+    if (errors_str == NULL) {
+        Py_CLEAR(buf);
+        Py_CLEAR(encoding_str);
+        goto error;
+    }
+
+    stream = _PyObject_CallMethodId(io, &PyId_TextIOWrapper, "OOOsOO",
+                                    buf, encoding_str, errors_str,
                                     newline, line_buffering, write_through);
     Py_CLEAR(buf);
+    Py_CLEAR(encoding_str);
+    Py_CLEAR(errors_str);
     if (stream == NULL)
         goto error;
 
@@ -1874,7 +1889,7 @@
     fd = fileno(stderr);
     std = create_stdio(config, iomod, fd, 1, "<stderr>",
                        config->stdio_encoding,
-                       "backslashreplace");
+                       L"backslashreplace");
     if (std == NULL)
         goto error;
 
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 0f7af2c..fbdeb9b 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -424,7 +424,7 @@
 {
     PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     const _PyCoreConfig *config = &interp->core_config;
-    return PyUnicode_FromString(config->filesystem_encoding);
+    return PyUnicode_FromWideChar(config->filesystem_encoding, -1);
 }
 
 /*[clinic input]
@@ -439,7 +439,7 @@
 {
     PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
     const _PyCoreConfig *config = &interp->core_config;
-    return PyUnicode_FromString(config->filesystem_errors);
+    return PyUnicode_FromWideChar(config->filesystem_errors, -1);
 }
 
 /*[clinic input]
@@ -1211,30 +1211,9 @@
 sys__enablelegacywindowsfsencoding_impl(PyObject *module)
 /*[clinic end generated code: output=f5c3855b45e24fe9 input=2bfa931a20704492]*/
 {
-    PyInterpreterState *interp = _PyInterpreterState_GET_UNSAFE();
-    _PyCoreConfig *config = &interp->core_config;
-
-    /* Set the filesystem encoding to mbcs/replace (PEP 529) */
-    char *encoding = _PyMem_RawStrdup("mbcs");
-    char *errors = _PyMem_RawStrdup("replace");
-    if (encoding == NULL || errors == NULL) {
-        PyMem_Free(encoding);
-        PyMem_Free(errors);
-        PyErr_NoMemory();
+    if (_PyUnicode_EnableLegacyWindowsFSEncoding() < 0) {
         return NULL;
     }
-
-    PyMem_RawFree(config->filesystem_encoding);
-    config->filesystem_encoding = encoding;
-    PyMem_RawFree(config->filesystem_errors);
-    config->filesystem_errors = errors;
-
-    if (_Py_SetFileSystemEncoding(config->filesystem_encoding,
-                                  config->filesystem_errors) < 0) {
-        PyErr_NoMemory();
-        return NULL;
-    }
-
     Py_RETURN_NONE;
 }