diff --git a/utils.rkt b/utils.rkt
index 3d9bcce..48db509 100644
--- a/utils.rkt
+++ b/utils.rkt
@@ -635,6 +635,8 @@
 ;;; or #:predicate/key.  #:predicate should be a function returning
 ;;; a Boolean result given a value of the hash value.  #:predicate
 ;;; should be a function taking a key and the corresponding value.
+;;;
+;;; The comparison predicate of ht determines the one for the result.
 (define (hash-filter
          ht
          #:predicate [predicate #f]