Error page 404 - secondary language

How to set up an error page (404) for a secondary language of a website?
I have a site for the primary language (se - Swedish), in the same tree I have the tree for the secondary language (en - English):

  • se (site - se)
    • page1 (se)
    • page2 (se)
    • en (en)
      • page1 (en)
      • page2 (en)

        I know how to configure the Error page for the (main) site, at the Edit Site view. But when an error occurs in the English part of the tree, the Swedish 404 page shows up. I would like to have an error page in English to show up instead for that part of the tree.
        Is this possible by configuration somehow or do I need to hack the Pimcore error handling?

I tried to create a site of the English part of the tree, having the domain “[domain]/en” and setting the Error page for the sub-site, but that didn’t work.

Running Pimcore 4