diff --git a/include/vis.h b/include/vis.h
index 30bd58a40425..22feaa99c065 100644
--- a/include/vis.h
+++ b/include/vis.h
@@ -87,6 +87,7 @@ char	*vis __P((char *, int, int, int));
 int	strvis __P((char *, const char *, int));
 int	strvisx __P((char *, const char *, size_t, int));
 int	strunvis __P((char *, const char *));
+int	strunvisx __P((char *, const char *, int));
 int	unvis __P((char *, int, int *, int));
 __END_DECLS