use correct system prompt formatting with chatml

app.py

@@ -70,7 +70,7 @@ def generate_response(message, history, initial_prompt, user_role, assistant_rol
     formatted_input = format_chat(chat_history, use_chatml)
 
     if use_chatml:
-        full_prompt = initial_prompt + "\n\n" + formatted_input + f"<|im_start|>{assistant_role}\n"
+        full_prompt = "<|im_start|>system\n" + initial_prompt + "<|im_end|>\n" + formatted_input + f"<|im_start|>{assistant_role}\n"
     else:
         full_prompt = initial_prompt + "\n\n" + formatted_input + f"<{assistant_role}>:"