PATCH /conversations/voice/{id}/participants failing with 400 on transfer

Trying to transfer a voice call to a different queue grammatically. The docs say to PATCH the participant with the to object, but I’m hitting a 400 Bad Request every time. I’ve verified the target queue ID exists and the user has the right permissions. Here’s the payload I’m sending:

{
 "to": {
 "id": "queue-12345",
 "type": "queue"
 }
}

The error body just says Invalid request body. Am I missing a required field like flowId or routingData? I’ve tried adding empty objects but it still fails. What’s the exact structure needed for a blind transfer to a queue?