diff --git a/discord-bot/api_client.py b/discord-bot/api_client.py
index 78f4f2ea..4e9ce612 100644
--- a/discord-bot/api_client.py
+++ b/discord-bot/api_client.py
@@ -66,8 +66,8 @@ class ApiClient:
     ) -> protocol_schema.Task:
         return self.fetch_task(protocol_schema.TaskRequestType.random, user, collective=collective)
 
-    def ack_task(self, task_id: str, post_id: str) -> None:
-        req = protocol_schema.TaskAck(message_id=post_id)
+    def ack_task(self, task_id: str, message_id: str) -> None:
+        req = protocol_schema.TaskAck(message_id=message_id)
         return self.post(f"/api/v1/tasks/{task_id}/ack", req.dict())
 
     def nack_task(self, task_id: str, reason: str) -> None: