Bitbucket - ERROR creating pull request with reviewers Edited

[Derbeerk]

I'm trying to create pull request in bitbucket via its API.

API description: https://developer.atlassian.com/bitbucket/api/2/reference/resource/repositories/%7Busername%7D/%7Brepo_slug%7D/pullrequests

This is an object I'm passing to the API

{
  username    : 'derbeerk',
  repo_slug   : 'lisatest',
  title       : 'title',
  description : 'description',
  source      : { branch: { name: '1_package' }},
  destination : { branch: { name: 'master'    }},
  reviewers   : '{13e7e98b-414b-4345-9a63-5a59d76f8032}'
}

In return I get an errors like this

StatusCodeError: 500 - {"type":"error","error":{"message":"'list'","id":"0436de5105664825bb69a5e80c65614d"}}

I tried to change reviewers to username, uuid without curly braces, add trailing comma, etc.. always got the same error in return.

P.S. If I remove reviewers property - pull request would be created perfectly fine