Quasar v2: Add form fields to q-uploader

I'm using the q-uploader element (https://quasar.dev/vue-components/uploader) with NodeJS in the backend.

I've been trying to add some additional form fields to the POST request, but it doesn't work. This is what I tried:

<q-uploader
  url="http://localhost:3000/api/upload/new"
  label="Max. size: 10 MB"
  accept=".pdf, image/*"
  max-file-size="10485760"
  with-credentials
  :form-fields="[{name: 'name', value: 'value'}]"
  @rejected="onRejected"
/>

The upload itself works OK but unfortunately without the additional form fields, as I can see from the network tab and also on the backend side. On NodeJS side:

router.post("/api/uploads/new", async (req, res) => {
  const form = new formidable.IncomingForm();
  console.log(req.body);  // returns {}
  console.log(form);  // returns the uploaded file
  ...
}

The request returns an empty document {}, however, the file arrives so in principle, it's working. What am I missing?

Thanks a lot!