diff --git a/src/llama_stack_client/lib/agents/react/agent.py b/src/llama_stack_client/lib/agents/react/agent.py
index bad7e46e..c71bd6ac 100644
--- a/src/llama_stack_client/lib/agents/react/agent.py
+++ b/src/llama_stack_client/lib/agents/react/agent.py
@@ -97,7 +97,7 @@ def get_tool_defs():
             agent_config = custom_agent_config
 
         if json_response_format:
-            agent_config.response_format = {
+            agent_config["response_format"] = {
                 "type": "json_schema",
                 "json_schema": ReActOutput.model_json_schema(),
             }