JSON POST headers

In a fetch for JSON POST adding these two headers:

let response = await fetch(url, {
    method: 'POST',
    body: JSON.stringify(data),
    headers:
    {
        'Content-Type': 'application/json',
        'Accept': 'text/plain', 
    }
});

returns a TypeError: Load failed message. But the target API needs both headers specified. Each header individually does not error, but the API doesn’t respond.

Any help appreciated.

Solved by using remoteFetchAsync instead of fetch.