diff --git a/library/include/wchar.h b/library/include/wchar.h
index e27b055..777ccba 100644
--- a/library/include/wchar.h
+++ b/library/include/wchar.h
@@ -168,7 +168,7 @@ extern int swprintf(wchar_t *s, const wchar_t *format, ...);
 
 extern int vfwprintf(FILE *stream,const wchar_t *format,va_list arg);
 extern int vwprintf(const wchar_t *format,va_list arg);
-extern int vswprintf(char *s, const wchar_t *format,va_list arg);
+extern int vswprintf(wchar_t *s, size_t maxlen, const wchar_t *format, va_list arg);
 
 /****************************************************************************/
 
diff --git a/library/wchar_vswprintf.c b/library/wchar_vswprintf.c
index b2773f6..b296bdb 100644
--- a/library/wchar_vswprintf.c
+++ b/library/wchar_vswprintf.c
@@ -38,7 +38,7 @@
 /****************************************************************************/
 
 int
-vswprintf(char *s, const wchar_t *format,va_list arg)
+vswprintf(wchar_t *s, size_t maxlen, const wchar_t *format, va_list arg)
 {
 	/* ZZZ unimplemented */
 	return(0);