diff --git a/src/unfurlbot/handlers/kafka.py b/src/unfurlbot/handlers/kafka.py
index 3a6185e..35eefc4 100644
--- a/src/unfurlbot/handlers/kafka.py
+++ b/src/unfurlbot/handlers/kafka.py
@@ -34,7 +34,7 @@ class SlackMessageContainer(BaseModel):
 )
 async def handle_slack_message(
     body: str,
-    msg: str = KafkaMessage,
+    msg: KafkaMessage,
     topic: str = Context("message.topic"),
 ) -> None:
     """Handle a Slack message."""