Michael Albinus <michael.albinus@gmx.de> writes:

> Glenn Morris <rgm@gnu.org> writes:
>
>> See also https://debbugs.gnu.org/34448 .
>>
>> I would guess Tramp isn't the only thing expecting system-name to be a string.
>
> Perhaps system-name returns better "localhost" but nil? Or at least the
> empty string, at build time with --no-build-details?

Since Tramp must also work for older Emacs versions, it needs an own fix
anyway.

Philipp, does the appended patch work for you?

Best regards, Michael.