diff --git a/include/sys/types.h b/include/sys/types.h
index b9e0d553..29c505fa 100644
--- a/include/sys/types.h
+++ b/include/sys/types.h
@@ -165,9 +165,15 @@ typedef unsigned uid_t;
 #ifndef __MES_WCHAR_T
 #define __MES_WCHAR_T
 #undef wchar_t
+// The compiler names the type of a wide character literal for its
+// target; MesCC names none.
+#ifdef __WCHAR_TYPE__
+typedef __WCHAR_TYPE__ wchar_t;
+#else
 typedef int wchar_t;
 #endif
 #endif
+#endif
 
 #endif // ! SYSTEM_LIBC
 
diff --git a/lib/stdio/vfprintf.c b/lib/stdio/vfprintf.c
index 839ad897..e1c1c971 100644
--- a/lib/stdio/vfprintf.c
+++ b/lib/stdio/vfprintf.c
@@ -23,6 +23,12 @@
 #include <stdio.h>
 #include <string.h>
 
+/* A compiler's own stdarg.h defines va_arg alone, and its va_arg reads a
+   double as one.  */
+#ifndef va_arg8
+#define va_arg8(ap, type) va_arg (ap, type)
+#endif
+
 int
 vfprintf (FILE * f, char const *format, va_list ap)
 {
diff --git a/lib/stdio/vsnprintf.c b/lib/stdio/vsnprintf.c
index ff1b3c2b..d8b3b5c8 100644
--- a/lib/stdio/vsnprintf.c
+++ b/lib/stdio/vsnprintf.c
@@ -23,6 +23,12 @@
 #include <stdarg.h>
 #include <string.h>
 
+/* A compiler's own stdarg.h defines va_arg alone, and its va_arg reads a
+   double as one.  */
+#ifndef va_arg8
+#define va_arg8(ap, type) va_arg (ap, type)
+#endif
+
 int
 vsnprintf (char *str, size_t size, char const *format, va_list ap)
 {