diff --git a/src/socketio/base_server.py b/src/socketio/base_server.py
index 1625b13e..c3b8591e 100644
--- a/src/socketio/base_server.py
+++ b/src/socketio/base_server.py
@@ -187,15 +187,18 @@ def rooms(self, sid, namespace=None):
         namespace = namespace or '/'
         return self.manager.get_rooms(sid, namespace)
 
-    def transport(self, sid):
+    def transport(self, sid, namespace=None):
         """Return the name of the transport used by the client.
 
         The two possible values returned by this function are ``'polling'``
         and ``'websocket'``.
 
         :param sid: The session of the client.
+        :param namespace: The Socket.IO namespace. If this argument is omitted
+                          the default namespace is used.
         """
-        return self.eio.transport(sid)
+        eio_sid = self.manager.eio_sid_from_sid(sid, namespace or '/')
+        return self.eio.transport(eio_sid)
 
     def get_environ(self, sid, namespace=None):
         """Return the WSGI environ dictionary for a client.
diff --git a/tests/async/test_server.py b/tests/async/test_server.py
index 256545eb..471e562a 100644
--- a/tests/async/test_server.py
+++ b/tests/async/test_server.py
@@ -307,9 +307,9 @@ def test_transport(self, eio):
         eio.return_value.send = AsyncMock()
         s = async_server.AsyncServer()
         s.eio.transport = mock.MagicMock(return_value='polling')
-        _run(s._handle_eio_connect('foo', 'environ'))
-        assert s.transport('foo') == 'polling'
-        s.eio.transport.assert_called_once_with('foo')
+        sid_foo = _run(s.manager.connect('123', '/foo'))
+        assert s.transport(sid_foo, '/foo') == 'polling'
+        s.eio.transport.assert_called_once_with('123')
 
     def test_handle_connect(self, eio):
         eio.return_value.send = AsyncMock()
diff --git a/tests/common/test_server.py b/tests/common/test_server.py
index 8f3a356b..b568c683 100644
--- a/tests/common/test_server.py
+++ b/tests/common/test_server.py
@@ -292,9 +292,9 @@ def test_send_eio_packet(self, eio):
     def test_transport(self, eio):
         s = server.Server()
         s.eio.transport = mock.MagicMock(return_value='polling')
-        s._handle_eio_connect('foo', 'environ')
-        assert s.transport('foo') == 'polling'
-        s.eio.transport.assert_called_once_with('foo')
+        sid_foo = s.manager.connect('123', '/foo')
+        assert s.transport(sid_foo, '/foo') == 'polling'
+        s.eio.transport.assert_called_once_with('123')
 
     def test_handle_connect(self, eio):
         s = server.Server()