Update 10.0.1 -> 10.0.2 fails with reverse proxy: override* config options ignored?

Dear nextcloud team & community!

First many thx for the nextcloud update!

When trying the nextcloud web-updater to upgrade from 10.0.1 to 10.0.2 it already fails with the very first step with

  Check for expected files
  Parsing response failed. 
  [omitted html syntax]
  404 Not Found. [...] 
  The requested URL /updater/index.php was not found on this server. [...] Server at host.com

The error gives me some indication what is wrong: The requested URL should be /nextcloud/updater/index.php .

The nextcloud server is running with nginx on subdomain.host.com/nextcloud . It is gated by a reverse proxy (apache) reachable via host.com/nextcloud/ .
This configuration runs well in normal operation with standard overwrite* config options set according to the nextcloud documentation.

Is an extra overwrite.updater.url (or similar) required for running the update on this kind of configuration, or might something else be misconfigured in my case?

Best regards and many thx!