diff --git a/src/or/dirserv.c b/src/or/dirserv.c
index f76a01a8eb..c2d3d8472c 100644
--- a/src/or/dirserv.c
+++ b/src/or/dirserv.c
@@ -743,6 +743,7 @@ static int generate_runningrouters(crypto_pk_env_t *private_key)
 /** Set *<b>rr</b> to the most recently generated encoded signed
  * running-routers list, generating a new one as necessary. */
 size_t dirserv_get_runningrouters(const char **rr)
+/* XXX008 Bug: size_t is unsigned, but we're returning -1 to mean error */
 {
   if (runningrouters_is_dirty) {
     if(generate_runningrouters(get_identity_key())) {