Flowable form people fieldType return string

Flowable Engine
1

I’m using https://www.flowable.org/docs/userguide/index.html#_task_actions to submit task with form. I’m submiting form below

{
    "name": "next_assignee",
    "value": {
        "id": "1",
        "firstName": "First Name",
        "lastName": "Last Name"
    }
}

But read the form returns

{
    "id": "next_assignee",
    "value": "{firstName=First Name, id=1, lastName=Last Name}"
}
2

I assume the people field returns user object in 6.4.1 but returns string in 6.4.2