diff --git a/library/charsio.yap b/library/charsio.yap
index eca9187de..313941196 100644
--- a/library/charsio.yap
+++ b/library/charsio.yap
@@ -31,6 +31,10 @@
 	with_output_to_chars/4
     ]).
 
+:- meta_predicate(with_output_to_chars(0,?)).
+:- meta_predicate(with_output_to_chars(0,-,?)).
+:- meta_predicate(with_output_to_chars(0,-,?,?)).
+
 format_to_chars(Form, Args, OUT) :-
 	format_to_chars(Form, Args, OUT, []).