diff --git a/changes/bug17153 b/changes/bug17153
new file mode 100644
index 0000000000..15a53c16f7
--- /dev/null
+++ b/changes/bug17153
@@ -0,0 +1,4 @@
+  o Minor bugfixes (test networks, IPv6):
+    - Allow internal IPv6 addresses in descriptors in test networks.
+      Fixes bug 17153; bugfix on 6b4af1071 in 0.2.3.16-alpha.
+      Patch by "teor", reported by "karsten".
diff --git a/src/or/router.c b/src/or/router.c
index 80732c9036..68bcf1326e 100644
--- a/src/or/router.c
+++ b/src/or/router.c
@@ -1941,7 +1941,11 @@ router_build_fresh_descriptor(routerinfo_t **r, extrainfo_t **e)
           ! p->server_cfg.no_advertise &&
           ! p->server_cfg.bind_ipv4_only &&
           tor_addr_family(&p->addr) == AF_INET6) {
-        if (! tor_addr_is_internal(&p->addr, 0)) {
+        /* Like IPv4, if the relay is configured using the default
+         * authorities, disallow internal IPs. Otherwise, allow them. */
+        const int default_auth = (!options->DirAuthorities &&
+                                  !options->AlternateDirAuthority);
+        if (! tor_addr_is_internal(&p->addr, 0) || ! default_auth) {
           ipv6_orport = p;
           break;
         } else {
@@ -1949,7 +1953,7 @@ router_build_fresh_descriptor(routerinfo_t **r, extrainfo_t **e)
           log_warn(LD_CONFIG,
                    "Unable to use configured IPv6 address \"%s\" in a "
                    "descriptor. Skipping it. "
-                   "Try specifying a globally reachable address explicitly. ",
+                   "Try specifying a globally reachable address explicitly.",
                    tor_addr_to_str(addrbuf, &p->addr, sizeof(addrbuf), 1));
         }
       }