diff --git a/zonedb.rkt b/zonedb.rkt
index 16b92f6..0644a7b 100644
--- a/zonedb.rkt
+++ b/zonedb.rkt
@@ -179,6 +179,7 @@
 ;; rr-set->list : SetOf<RR> -> ListOf<RR>
 ;; Like set->list, but places all CNAME records first.
 ;; This is apparently to work around bugs in old versions of BIND?
+;; TODO: Perhaps the CNAMEs even need to be in topologically-sorted order?
 (define (rr-set->list rrs)
   (append (set->list (filter-by-type rrs 'cname))
 	  (set->list (set-filter (lambda (rr) (not (eqv? (rr-type rr) 'cname))) rrs))))