diff --git a/Include/unicodeobject.h b/Include/unicodeobject.h
--- a/Include/unicodeobject.h
+++ b/Include/unicodeobject.h
@@ -109,6 +109,10 @@ Copyright (c) Corporation for National R
 # endif
 #endif
 
+#if defined(MS_WINDOWS) && defined(HAVE_USABLE_WCHAR_T)
+#  define HAVE_MBCS
+#endif
+
 #ifdef HAVE_WCHAR_H
 /* Work around a cosmetic bug in BSDI 4.x wchar.h; thanks to Thomas Wouters */
 # ifdef _HAVE_BSDI
@@ -1162,7 +1166,7 @@ PyAPI_FUNC(PyObject *) PyUnicode_Transla
     );
 #endif
 
-#ifdef MS_WIN32
+#ifdef HAVE_MBCS
 
 /* --- MBCS codecs for Windows -------------------------------------------- */
 
@@ -1191,7 +1195,7 @@ PyAPI_FUNC(PyObject*) PyUnicode_EncodeMB
     );
 #endif
 
-#endif /* MS_WIN32 */
+#endif /* HAVE_MBCS */
 
 /* --- Decimal Encoder ---------------------------------------------------- */
 
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -1506,7 +1506,7 @@ PyUnicode_Decode(const char *s,
                  (strcmp(lower, "latin1") == 0) ||
                  (strcmp(lower, "iso-8859-1") == 0))
             return PyUnicode_DecodeLatin1(s, size, errors);
-#if defined(MS_WINDOWS) && defined(HAVE_USABLE_WCHAR_T)
+#ifdef HAVE_MBCS
         else if (strcmp(lower, "mbcs") == 0)
             return PyUnicode_DecodeMBCS(s, size, errors);
 #endif
@@ -1848,7 +1848,7 @@ PyUnicode_DecodeFSDefault(const char *s)
 PyObject*
 PyUnicode_DecodeFSDefaultAndSize(const char *s, Py_ssize_t size)
 {
-#if defined(MS_WINDOWS) && defined(HAVE_USABLE_WCHAR_T)
+#ifdef HAVE_MBCS
     return PyUnicode_DecodeMBCS(s, size, NULL);
 #elif defined(__APPLE__)
     return PyUnicode_DecodeUTF8(s, size, "surrogateescape");
@@ -4942,7 +4942,7 @@ PyUnicode_AsASCIIString(PyObject *unicod
                                  NULL);
 }
 
-#if defined(MS_WINDOWS) && defined(HAVE_USABLE_WCHAR_T)
+#ifdef HAVE_MBCS
 
 /* --- MBCS codecs for Windows -------------------------------------------- */
 
@@ -5229,7 +5229,7 @@ PyUnicode_AsMBCSString(PyObject *unicode
 
 #undef NEED_RETRY
 
-#endif /* MS_WINDOWS */
+#endif /* HAVE_MBCS */
 
 /* --- Character Mapping Codec -------------------------------------------- */
 
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -18,7 +18,7 @@
    Don't forget to modify PyUnicode_DecodeFSDefault() if you touch any of the
    values for Py_FileSystemDefaultEncoding!
 */
-#if defined(MS_WINDOWS) && defined(HAVE_USABLE_WCHAR_T)
+#ifdef HAVE_MBCS
 const char *Py_FileSystemDefaultEncoding = "mbcs";
 int Py_HasFileSystemDefaultEncoding = 1;
 #elif defined(__APPLE__)