Unable to update meeting using Meetings API. Error: MET-109 [meeting_capacity] is not specified

We're developing a 3rd party integration using the Meetings REST API. All good and well with the exception of updating existing meetings. Here's the API request:

PUT https://platform.devtest.ringcentral.com/restapi/v1.0/account/~/extension/~/meeting/[redacted meetingId] HTTP/1.1
Accept: application/json
Authorization: Bearer [redacted token]
Content-Type: application/json; charset=utf-8
Host: platform.devtest.ringcentral.com
Content-Length: 400
Expect: 100-continue
Accept-Encoding: gzip, deflate

{
  "topic": "[update] Test ran on 12/10/2017 12:35 AM UTC",
  "schedule": {
    "startTime": "2018-01-10T01:30:00Z",
    "durationInMinutes": 90,
    "timeZone": {
      "id": "1"
    }
  },
  "meetingType": "Scheduled",
  "allowJoinBeforeHost": false,
  "startHostVideo": false,
  "startParticipantsVideo": false,
  "audioOptions": [
    "Phone",
    "ComputerAudio"
  ]
}

And the response:

HTTP/1.1 503 Service Unavailable
Server: nginx/1.10.2
Date: Sun, 10 Dec 2017 01:00:01 GMT
Content-Type: application/json;charset=UTF-8
Content-Length: 479
Connection: keep-alive
RCRequestId: 724c5008-dd45-11e7-97a3-005056bb26b9
RoutingKey: SJC11P01PAS02
Content-Language: en-US
X-Rate-Limit-Group: medium
X-Rate-Limit-Limit: 40
X-Rate-Limit-Remaining: 39
X-Rate-Limit-Window: 60
Retry-After: 40

{
  "errorCode" : "MET-109",
  "message" : "Cannot update meeting. Reason : [Response validation failure: [meeting_capacity] is not specified]",
  "errors" : [ {
    "errorCode" : "MET-109",
    "message" : "Cannot update meeting. Reason : [Response validation failure: [meeting_capacity] is not specified]",
    "reason" : "Response validation failure: [meeting_capacity] is not specified"
  } ],
  "reason" : "Response validation failure: [meeting_capacity] is not specified"
}

The problem is that there no documentation mentioning "meeting_capacity" parameter, when it should be sent and what values it needs to have.