diff --git a/src/or/router.c b/src/or/router.c
index 5b7b01c130..24c8278367 100644
--- a/src/or/router.c
+++ b/src/or/router.c
@@ -842,6 +842,7 @@ router_rebuild_descriptor(int force)
        tor_free(name);
      });
 
+    /* remove duplicates from the list */
     smartlist_sort_strings(ri->declared_family);
     for (i = 1; i < smartlist_len(ri->declared_family); ++i) {
       const char *a, *b;