diff --git a/src/wormhole/server/rendezvous_websocket.py b/src/wormhole/server/rendezvous_websocket.py
index 1000b0d..d6585bb 100644
--- a/src/wormhole/server/rendezvous_websocket.py
+++ b/src/wormhole/server/rendezvous_websocket.py
@@ -161,7 +161,7 @@ class WebSocketRendezvous(websocket.WebSocketServerProtocol):
 
     def send(self, mtype, **kwargs):
         kwargs["type"] = mtype
-        kwargs["sent"] = time.time()
+        kwargs["server_tx"] = time.time()
         payload = json.dumps(kwargs).encode("utf-8")
         self.sendMessage(payload, False)
 
diff --git a/src/wormhole/test/test_server.py b/src/wormhole/test/test_server.py
index 71a1239..a9eb684 100644
--- a/src/wormhole/test/test_server.py
+++ b/src/wormhole/test/test_server.py
@@ -685,8 +685,8 @@ class WebSocketAPI(ServerBase, unittest.TestCase):
         self.assertEqual(msg["type"], "message")
         self.assertEqual(strip_message(msg["message"]),
                          {"phase": "1", "body": "msg1A"})
-        self.assertIn("sent", msg)
-        self.assertIsInstance(msg["sent"], float)
+        self.assertIn("server_tx", msg)
+        self.assertIsInstance(msg["server_tx"], float)
 
         c1.send(u"add", phase="1", body="msg1B")
         c1.send(u"add", phase="2", body="msg2A")
diff --git a/src/wormhole/twisted/transcribe.py b/src/wormhole/twisted/transcribe.py
index b2d34fb..d6a7c5d 100644
--- a/src/wormhole/twisted/transcribe.py
+++ b/src/wormhole/twisted/transcribe.py
@@ -140,7 +140,7 @@ class Wormhole:
         return meth(msg)
 
     def _ws_handle_welcome(self, msg):
-        self._timing.add("welcome").server_sent(msg["sent"])
+        self._timing.add("welcome").server_sent(msg["server_tx"])
         welcome = msg["welcome"]
         if ("motd" in welcome and
             not self.motd_displayed):
@@ -191,7 +191,7 @@ class Wormhole:
         self._wakeup()
 
     def _ws_handle_error(self, msg):
-        self._timing.add("error").server_sent(msg["sent"])
+        self._timing.add("error").server_sent(msg["server_tx"])
         err = ServerError("%s: %s" % (msg["error"], msg["orig"]),
                           self._ws_url)
         return self._signal_error(err)
@@ -224,7 +224,7 @@ class Wormhole:
         returnValue(code)
 
     def _ws_handle_allocated(self, msg):
-        self._allocate_t.server_sent(msg["sent"])
+        self._allocate_t.server_sent(msg["server_tx"])
         if self._channelid is not None:
             return self._signal_error("got duplicate channelid")
         self._channelid = msg["channelid"]