Html export for CLI: missing module "theme.js"

I am trying to export a notebook to html using the CLI, but it fails with the error message

$> joplin export . --format html --log-level debug
Cannot find module '../../theme.js'

I have checked the log for relevant error messages, but to no avail. I also checked if I could find theme.js somewhere, but the only path is /usr/lib/node_modules/npm/docs/src/theme.js which seems not related to this issue.

Any idea on how to continue debugging?

I am running 1.0.163 (prod) on Ubuntu 18.04 for WSL.
I use nodejs v10.20.1 and npm version 6.14.4

Could you add a bug report on GitHub about it?