diff --git a/python/samples/agentchat_fastapi/app_agent.py b/python/samples/agentchat_fastapi/app_agent.py
index 9f114a651655..4a0afd6ad71f 100644
--- a/python/samples/agentchat_fastapi/app_agent.py
+++ b/python/samples/agentchat_fastapi/app_agent.py
@@ -88,8 +88,8 @@ async def chat(request: TextMessage) -> TextMessage:
 
         # Save chat history to file.
         history = await get_history()
-        history.append(request.model_dump())
-        history.append(response.chat_message.model_dump())
+        history.append(request.dump())
+        history.append(response.chat_message.dump())
         async with aiofiles.open(history_path, "w") as file:
             await file.write(json.dumps(history))
 
diff --git a/python/samples/agentchat_fastapi/app_team.py b/python/samples/agentchat_fastapi/app_team.py
index a67ce3c4f19c..4f32badff6d2 100644
--- a/python/samples/agentchat_fastapi/app_team.py
+++ b/python/samples/agentchat_fastapi/app_team.py
@@ -121,10 +121,10 @@ async def _user_input(prompt: str, cancellation_token: CancellationToken | None)
                 async for message in stream:
                     if isinstance(message, TaskResult):
                         continue
-                    await websocket.send_json(message.model_dump())
+                    await websocket.send_json(message.dump())
                     if not isinstance(message, UserInputRequestedEvent):
                         # Don't save user input events to history.
-                        history.append(message.model_dump())
+                        history.append(message.dump())
 
                 # Save team state to file.
                 async with aiofiles.open(state_path, "w") as file: