diff --git a/docs/source/guides.rst b/docs/source/guides.rst
index 4df78c0..83b0334 100644
--- a/docs/source/guides.rst
+++ b/docs/source/guides.rst
@@ -148,7 +148,7 @@ Here is the naive way to implement concatenation:
             # Called for the simple case when a frame is a whole message
             pass
 
-        def on_concatenated_message(self, msg_type: picows.WSMsgType, payload: bytearray):
+        def on_concatenated_message(self, transport: picows.WSTransport, msg_type: picows.WSMsgType, payload: bytearray):
             # Called after concatenating a message from multiple frames
             pass