diff --git a/private_gpt/components/llm/prompt_helper.py b/private_gpt/components/llm/prompt_helper.py
index 985d217b..3e452216 100644
--- a/private_gpt/components/llm/prompt_helper.py
+++ b/private_gpt/components/llm/prompt_helper.py
@@ -173,18 +173,20 @@ class TagPromptStyle(AbstractPromptStyle):
 
 class MistralPromptStyle(AbstractPromptStyle):
     def _messages_to_prompt(self, messages: Sequence[ChatMessage]) -> str:
-        prompt = "<s>"
+        inst_buffer = []
+        text = ""
         for message in messages:
-            role = message.role
-            content = message.content or ""
-            if role.lower() == "system":
-                message_from_user = f"[INST] {content.strip()} [/INST]"
-                prompt += message_from_user
-            elif role.lower() == "user":
-                prompt += "</s>"
-                message_from_user = f"[INST] {content.strip()} [/INST]"
-                prompt += message_from_user
-        return prompt
+            if message.role == MessageRole.SYSTEM:
+                inst_buffer.append(message.content.strip())
+            elif message.role == MessageRole.USER:
+                inst_buffer.append(message.content.strip())
+                text += "<s>[/INST] " + "\n".join(inst_buffer) + " [/INST]"
+                inst_buffer.clear()
+            elif message.role == MessageRole.ASSISTANT:
+                text += " " + message.content.strip() + "</s>"
+            else:
+                raise ValueError(f"Unknown message role {message.role}")
+        return text
 
     def _completion_to_prompt(self, completion: str) -> str:
         return self._messages_to_prompt(