PATCH /api/v2/conversations/calls/{id} transfer failing with 400

Trying to transfer an active call to a different queue using the Conversations API. The request hits the endpoint but returns a 400 Bad Request. Here’s the payload:

{
 "to": {
 "id": "queue-id-123",
 "type": "queue"
 },
 "transferType": "blind"
}

Docs say this structure is valid, but Genesys is rejecting it. Am I missing a required field?