diff --git a/log10/_httpx_utils.py b/log10/_httpx_utils.py
index 84a8062..3952472 100644
--- a/log10/_httpx_utils.py
+++ b/log10/_httpx_utils.py
@@ -153,6 +153,10 @@ async def _try_post_request_async(url: str, payload: dict = {}) -> httpx.Respons
 
 
 def format_anthropic_request(request_content) -> str:
+    system_message = request_content.get("system", "")
+    if system_message:
+        request_content["messages"].insert(0, {"role": "system", "content": system_message})
+
     for message in request_content.get("messages", []):
         new_content = []
         message_content = message.get("content")
diff --git a/tests/test_anthropic.py b/tests/test_anthropic.py
index ec30111..015b646 100644
--- a/tests/test_anthropic.py
+++ b/tests/test_anthropic.py
@@ -31,18 +31,22 @@ def test_completions_create(session, anthropic_legacy_model):
 @pytest.mark.chat
 def test_messages_create(session, anthropic_model):
     client = Anthropic()
-
+    system_message = "Respond only in Yoda-speak."
     message = client.messages.create(
         model=anthropic_model,
         max_tokens=1000,
         temperature=0.0,
-        system="Respond only in Yoda-speak.",
+        system=system_message,
         messages=[{"role": "user", "content": "How are you today?"}],
     )
 
     text = message.content[0].text
     assert isinstance(text, str)
-    _LogAssertion(completion_id=session.last_completion_id(), message_content=text).assert_chat_response()
+    log_assertion = _LogAssertion(
+        completion_id=session.last_completion_id(), message_content=text, system_message=system_message
+    )
+    log_assertion.assert_chat_response()
+    log_assertion.assert_system_message_request()
 
 
 @pytest.mark.chat
diff --git a/tests/utils.py b/tests/utils.py
index 534d855..b259015 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -25,6 +25,7 @@ def __init__(self, *args, **kwargs):
         self._message_content = kwargs.get("message_content", "")
         self._text = kwargs.get("text", "")
         self._function_args = kwargs.get("function_args", [])
+        self._system_message = kwargs.get("system_message", "")
 
         assert self._completion_id, "No completion id provided."
         assert is_valid_uuid(self._completion_id), "Completion ID should be found and valid uuid."
@@ -52,6 +53,23 @@ def assert_text_response(self):
             self._text == text
         ), f"Text does not match the generated completion for completion {self._completion_id}."
 
+    def assert_system_message_request(self):
+        if not self._system_message:
+            return
+
+        self.get_completion()
+        assert self.data.get("request", {}), f"No request logged for completion {self._completion_id}."
+        request = self.data["request"]
+        assert request.get("messages", ""), f"No request message logged for completion {self._completion_id}."
+        system_message = request["messages"][0]
+        assert system_message.get(
+            "content", ""
+        ), f"No system message content logged for completion {self._completion_id}."
+        content = system_message["content"]
+        assert (
+            self._system_message == content
+        ), f"System message content does not match the generated completion for completion {self._completion_id}."
+
     def assert_chat_response(self):
         assert self._message_content, "No output generated from the model."
         self.get_completion()