diff --git a/collects/handin-server/main.ss b/collects/handin-server/main.ss
index 1365816a05..8d08230fc1 100644
--- a/collects/handin-server/main.ss
+++ b/collects/handin-server/main.ss
@@ -94,6 +94,7 @@
                (copy-directory/files dir/f f)]
               [(or (<= (file-or-directory-modify-seconds f)
                        (file-or-directory-modify-seconds dir/f))
+                   ;; just in case, check the size too:
                    (and (file-exists? f) (file-exists? dir/f)
                         (not (= (file-size f) (file-size dir/f)))))
                ;; f is newer in dir than in the working directory