Index: dates.rkt
==================================================================
--- dates.rkt
+++ dates.rkt
@@ -42,9 +42,9 @@
 
   ;; How we handle weird input
   (check-equal? (ymd->english "2018-08-12 everything after 1st space ignored") "August 12, 2018")
   (check-equal? (ymd->english "2018-08 omitting the day") "August 1, 2018")
   (check-equal? (ymd->english "2018 omitting month and day") "January 1, 2018")
-  (check-equal? (ymd->dateformat "2018-08-12") "123")
+  (check-equal? (ymd->dateformat "2018-08-12" "123") "123")
 
   ;; Stuff we just don't handle
   (check-exn exn:gregor:parse? (lambda () (ymd->english "2018-xyz"))))