diff --git a/llm/default_plugins/openai_models.py b/llm/default_plugins/openai_models.py
index b821cdd..2093467 100644
--- a/llm/default_plugins/openai_models.py
+++ b/llm/default_plugins/openai_models.py
@@ -337,8 +337,13 @@ class Completion(Chat):
         messages = []
         if conversation is not None:
             for prev_response in conversation.responses:
+                # We add system prompts in Markdown bold
+                if prev_response.prompt.system:
+                    messages.append("**{}**".format(prev_response.prompt.system))
                 messages.append(prev_response.prompt.prompt)
                 messages.append(prev_response.text())
+        if prompt.system:
+            messages.append("**{}**".format(prompt.system))
         messages.append(prompt.prompt)
         response._prompt_json = {"messages": messages}
         kwargs = self.build_kwargs(prompt)
diff --git a/tests/test_llm.py b/tests/test_llm.py
index 7758180..bb5088d 100644
--- a/tests/test_llm.py
+++ b/tests/test_llm.py
@@ -301,7 +301,8 @@ def test_openai_chat_stream(mocked_openai_chat_stream, user_path):
     assert result.output == "Hi.\n"
 
 
-def test_openai_completion(mocked_openai_completion, user_path):
+@pytest.mark.parametrize("system", (None, "a system prompt"))
+def test_openai_completion(mocked_openai_completion, user_path, system):
     log_path = user_path / "logs.db"
     log_db = sqlite_utils.Database(str(log_path))
     log_db["responses"].delete_where()
@@ -315,28 +316,32 @@ def test_openai_completion(mocked_openai_completion, user_path):
             "--no-stream",
             "--key",
             "x",
-        ],
+        ]
+        + (["--system", system] if system else []),
         catch_exceptions=False,
     )
     assert result.exit_code == 0
     assert result.output == "\n\nThis is indeed a test\n"
 
     # Should have requested 256 tokens
+    expected_prompt = "Say this is a test"
+    if system:
+        expected_prompt = "**a system prompt**\n" + expected_prompt
     assert json.loads(mocked_openai_completion.last_request.text) == {
         "model": "gpt-3.5-turbo-instruct",
-        "prompt": "Say this is a test",
+        "prompt": expected_prompt,
         "stream": False,
         "max_tokens": 256,
     }
-
+    expected_messages = json.dumps(expected_prompt.split("\n"))
     # Check it was logged
     rows = list(log_db["responses"].rows)
     assert len(rows) == 1
     expected = {
         "model": "gpt-3.5-turbo-instruct",
         "prompt": "Say this is a test",
-        "system": None,
-        "prompt_json": '{"messages": ["Say this is a test"]}',
+        "system": system,
+        "prompt_json": '{"messages": ' + expected_messages + "}",
         "options_json": "{}",
         "response": "\n\nThis is indeed a test",
     }