diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 1e9868a..4da984f 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -16,7 +16,7 @@
 /* The default encoding used by the platform file system APIs
    Can remain NULL for all platforms that don't have such a concept
 */
-#ifdef MS_WIN32
+#if defined(MS_WIN32) && defined(HAVE_USABLE_WCHAR_T)
 const char *Py_FileSystemDefaultEncoding = "mbcs";
 #else
 const char *Py_FileSystemDefaultEncoding = NULL; /* use default */