diff --git a/collects/typed-racket/optimizer/tool/report.rkt b/collects/typed-racket/optimizer/tool/report.rkt
index 01aee338f5..d794c9af71 100644
--- a/collects/typed-racket/optimizer/tool/report.rkt
+++ b/collects/typed-racket/optimizer/tool/report.rkt
@@ -90,6 +90,8 @@
                          0
                          (missed-opt-log-entry-badness l)))]
       [_ #f])) ; no source location, ignore
+  ;; We remove duplicates that were caused by traversing the same piece
+  ;; of code multiple times in the optimizer.
   (filter values (map log-entry->report-entry (remove-duplicates log))))
 
 (define (merge-entries prev l)