PATCH /api/v2/interactions/{id}/participants 400 on queue transfer

Trying to transfer a voice call to another queue programmatically. Sending a PATCH to /api/v2/interactions/{id}/participants with the new target in the JSON. Getting a 400 Bad Request back immediately. The docs say to use the ‘transfer’ action but the payload keeps getting rejected. Here is the JSON I am sending. What is wrong with it?

{
 "action": "transfer",
 "target": {
 "id": "queue-id-here",
 "type": "queue"
 }
}