How to auto-height an Image using only a width?

[opendeluxe]

As already written here (vercel/nextjs-portfolio-starter#32) at the base template, I want to put images into a blog post with a fixed width but an automatically calculated height. How to do that?

Using code like

<Image
  src="/photos/test.jpg"
  alt="Photo"
  width={200}
  priority
  className="next-image"
/>

will return the error message:

Error: Image with src "/photos/test.jpg" must use "width" and "height" properties or "layout='fill'" property.

The property "layout=fill" doesn't work either, as it strechtes the image over the full screen size.

any ideas how to do that?