diff --git a/mem0/llms/ollama.py b/mem0/llms/ollama.py
index 74d59c0d1..af976dc24 100644
--- a/mem0/llms/ollama.py
+++ b/mem0/llms/ollama.py
@@ -119,11 +119,12 @@ class OllamaLLM(LLMBase):
         # Handle JSON response format by using Ollama's native format parameter
         if response_format and response_format.get("type") == "json_object":
             params["format"] = "json"
-            # Also add JSON format instruction to the last message as a fallback
+            messages = [dict(m) for m in messages]
             if messages and messages[-1]["role"] == "user":
                 messages[-1]["content"] += "\n\nPlease respond with valid JSON only."
             else:
                 messages.append({"role": "user", "content": "Please respond with valid JSON only."})
+            params["messages"] = messages
 
         # Add options for Ollama (temperature, num_predict, top_p)
         options = {