How to return 304 status in express?

Question

Express.js

I wrote a condition to return a 304 status and added a test header to see if my condition actually works.

app.get('/', (req, res, next) => {
  const modifiedSince = req.get('If-Modified-Since')
  
  if (modifiedSince) {
    res.append('Test-Header', '*');
    res.status(304).end();
  } else {
    res.sendFile(path.join(__dirname + '/index.html'));
  }
})

The title is added (screenshot - joxi.ru/EA4GNNzhv1ld32), but the status code is still 200, why is that?