diff --git a/src/wormhole_transit_relay/server_tap.py b/src/wormhole_transit_relay/server_tap.py
index 718759e..d3e3f56 100644
--- a/src/wormhole_transit_relay/server_tap.py
+++ b/src/wormhole_transit_relay/server_tap.py
@@ -19,7 +19,7 @@ class Options(usage.Options):
     longdesc = LONGDESC
 
     optParameters = [
-        ("port", "p", "tcp:4001", "endpoint to listen on"),
+        ("port", "p", "tcp:4001:interface=\:\:1", "endpoint to listen on"),
         ("blur-usage", None, None, "blur timestamps and data sizes in logs"),
         ("log-fd", None, None, "write JSON usage logs to this file descriptor"),
         ("usage-db", None, None, "record usage data (SQLite)"),
diff --git a/src/wormhole_transit_relay/test/test_config.py b/src/wormhole_transit_relay/test/test_config.py
index 02e3fee..6eb5dc2 100644
--- a/src/wormhole_transit_relay/test/test_config.py
+++ b/src/wormhole_transit_relay/test/test_config.py
@@ -2,17 +2,19 @@ from __future__ import unicode_literals, print_function
 from twisted.trial import unittest
 from .. import server_tap
 
+PORT = "tcp:4001:interface=\:\:1"
+
 class Config(unittest.TestCase):
     def test_defaults(self):
         o = server_tap.Options()
         o.parseOptions([])
         self.assertEqual(o, {"blur-usage": None, "log-fd": None,
-                             "usage-db": None, "port": "tcp:4001"})
+                             "usage-db": None, "port": PORT})
     def test_blur(self):
         o = server_tap.Options()
         o.parseOptions(["--blur-usage=60"])
         self.assertEqual(o, {"blur-usage": 60, "log-fd": None,
-                             "usage-db": None, "port": "tcp:4001"})
+                             "usage-db": None, "port": PORT})
 
     def test_string(self):
         o = server_tap.Options()