diff --git a/extra/builder/util/util.factor b/extra/builder/util/util.factor
index a838eced6d..1081d3256d 100644
--- a/extra/builder/util/util.factor
+++ b/extra/builder/util/util.factor
@@ -4,7 +4,7 @@ USING: kernel words namespaces classes parser continuations
        math math.parser
        combinators sequences splitting quotations arrays strings tools.time
        parser-combinators new-slots accessors assocs.lib
-       combinators.cleave bake calendar  ;
+       combinators.cleave bake calendar calendar.format ;
 
 IN: builder.util