diff --git a/doc/dir-spec.txt b/doc/dir-spec.txt
index 2cbc7b981e..70c164af32 100644
--- a/doc/dir-spec.txt
+++ b/doc/dir-spec.txt
@@ -450,7 +450,10 @@ $Id$
    known running, valid routers.
 
    "Guard" -- A router is a possible 'Guard' if it is 'Stable' and its
-   bandwidth is above median for known running, valid routers.
+   bandwidth is above median for known running, valid routers.  If the total
+   bandwidth of Running Valid non-BadExit Exit servers is less than one third
+   of the total bandwidth of all Running Valid servers, no Exit is listed as
+   a Guard.
 
    "Authority" -- A router is called an 'Authority' if the authority
    generating the network-status document believes it is an authority.
diff --git a/src/or/dirserv.c b/src/or/dirserv.c
index c7f0462a3e..0515878e04 100644
--- a/src/or/dirserv.c
+++ b/src/or/dirserv.c
@@ -1362,7 +1362,6 @@ dirserv_compute_performance_thresholds(routerlist_t *rl)
       total_bandwidth += *bw;
       if (ri->is_exit && !ri->is_bad_exit)
         total_exit_bandwidth += *bw;
-      /* XXXX012 Document the one-third behavior in dir-spec.txt. */
       smartlist_add(bandwidths, bw);
     }
   });