diff --git a/src/or/dirserv.c b/src/or/dirserv.c
index d9bea6eb9a..639839973a 100644
--- a/src/or/dirserv.c
+++ b/src/or/dirserv.c
@@ -568,6 +568,7 @@ format_versions_list(config_line_t *ln)
     smartlist_split_string(versions, ln->value, ",",
                            SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, 0);
   }
+  smartlist_sort_strings(versions); /* sort them */
   result = smartlist_join_strings(versions,",",0,NULL);
   SMARTLIST_FOREACH(versions,char *,s,tor_free(s));
   smartlist_free(versions);