Content-Disposition Header name must be a valid HTTP token on Node

So in my server, I'm trying to set an header, which in this case is this:

res.setHeader({
 'Content-Disposition': 'attachment; filename=' + req.params.filename + '.pdf',
});

I'm using this so when I download the file I get the name on the client, but is not working for now, I get this weird error message:

TypeError [ERR_INVALID_HTTP_TOKEN]: Header name must be a valid HTTP token ["{
  'Content-Disposition': 'attachment; filename=0.7105216890033654.pdf'
}"]

Here is extra understanding, I'm trying to download the file that is being send from server.

Here is the full handling on server:

downloadInvoice: (req, res) => {
res.setHeader({
 'Content-Disposition': 'attachment; filename=' + req.params.filename + '.pdf',
    });
    res.download(`${path}/${req.params.filename}.pdf`,
      (err) => {
        fs.unlinkSync(`${path}/${req.params.filename}.pdf`);
      }
    );

And here is how I'm handling it on the front:

fetch(`${api}/orders/download/${res.payload.filename}`, {
          responseType: 'blob',
          'Content-Type': 'application/pdf',
        })
          .then((res) => downloadFile(res))
          .catch((err) => console.log(err));

        const downloadFile = async (res) => {
          const url = window.URL.createObjectURL(await res.blob());
          const link = document.createElement('a');
          link.href = url;
          link.setAttribute('download', `${filename}.pdf`);
          document.body.appendChild(link);
          link.click();
        };