diff --git a/contrib/parser-combinators/parser-combinators.factor b/contrib/parser-combinators/parser-combinators.factor
index 621491c63b..9c756a4950 100644
--- a/contrib/parser-combinators/parser-combinators.factor
+++ b/contrib/parser-combinators/parser-combinators.factor
@@ -27,6 +27,7 @@ USE: sequences
 USE: strings
 USE: lists
 USE: math
+USE: io
 
 GENERIC: phead