diff --git a/letsencrypt/client/standalone_authenticator.py b/letsencrypt/client/standalone_authenticator.py
index 3e9a4381c..c4a1c63b1 100644
--- a/letsencrypt/client/standalone_authenticator.py
+++ b/letsencrypt/client/standalone_authenticator.py
@@ -281,9 +281,13 @@ class StandaloneAuthenticator(object):
             if proc.wait() != 0:
                 raise OSError("netstat subprocess failed")
             lines = [x.split() for x in stdout.split("\n")[2:] if x]
-            listeners = [L[6] for L in lines if L[0] == 'tcp' \
-                         and L[5] == 'LISTEN' \
-                         and L[3] == '0.0.0.0:{0}'.format(port)]
+            listeners = [L[6] for L in lines if
+                         # IPv4 socket case
+                         (L[0] == 'tcp' and L[5] == 'LISTEN' \
+                         and L[3] == '0.0.0.0:{0}'.format(port)) or \
+                         # IPv6 socket case
+                         (L[0] == 'tcp6' and L[5] == 'LISTEN' \
+                         and L[3] == ':::{0}'.format(port))]
             if listeners:
                 pid, name = listeners[0].split("/")
                 display = zope.component.getUtility(interfaces.IDisplay)
diff --git a/letsencrypt/client/tests/standalone_authenticator_test.py b/letsencrypt/client/tests/standalone_authenticator_test.py
index 940ead6d0..9787073b1 100644
--- a/letsencrypt/client/tests/standalone_authenticator_test.py
+++ b/letsencrypt/client/tests/standalone_authenticator_test.py
@@ -231,6 +231,25 @@ tcp        0      0 0.0.0.0:1728            0.0.0.0:*               LISTEN
         self.assertTrue(result)
         self.assertEqual(mock_get_utility.call_count, 1)
 
+    @mock.patch("letsencrypt.client.standalone_authenticator.subprocess.Popen")
+    @mock.patch("letsencrypt.client.standalone_authenticator."
+                "zope.component.getUtility")
+    def test_has_relevant_ipv6_line(self, mock_get_utility, mock_popen):
+        # pylint: disable=line-too-long,trailing-whitespace
+        subprocess_object = mock.MagicMock()
+        subprocess_object.communicate.return_value = (
+            """Active Internet connections (servers and established)
+Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name
+tcp        0      0 127.0.1.1:53            0.0.0.0:*               LISTEN      1234/foo        
+tcp        0      0 127.0.0.1:631           0.0.0.0:*               LISTEN      2345/bar        
+tcp6       0      0 :::17                   :::*                    LISTEN      11111/hello     
+tcp        0      0 0.0.0.0:1728            0.0.0.0:*               LISTEN      2345/bar        """,
+            "I am the standard error")
+        subprocess_object.wait.return_value = 0
+        mock_popen.return_value = subprocess_object
+        result = self.authenticator.already_listening(17)
+        self.assertTrue(result)
+        self.assertEqual(mock_get_utility.call_count, 1)
 
 class PerformTest(unittest.TestCase):
     """Tests for perform() method."""