swr fetcher configuration ignored

I use swr to fetch user data. The request is accompanied by cookies.

The fetcher is configured for cors request as follow:

const fetcher = async (url: string, params?: any) => {
  const res = await fetch(url, fetchConfig)

  return handleResponse(res)
}

with fetchConfig as:

{
  credentials: 'include',
  mode: 'cors'
}

The first request is sent correctly with cookies, but the subsequent requests are sent without cookies, which results in failed(401) request.

I browsed the network tab of browser console and found out that:

• The first request is "initiated" by above fetcher snippet.
• The subsequent requests are "initiated" by web-preset.js as follows:

var fetcher = function (url) { return fetch(url).then(function (res) { return res.json(); }); };

Notice it's not using the configuration. Does anybody have an idea why this is happening, or why the configured fetcher is not used at all except the first time?