Xbindkeys no longer working after system update (Guile and encoding related)

A few system updates ago on my slackware64-current, Xbindkeys 1.8.7 stopped working with the following error:

Quote:

Pre-boot error; key: encoding-error, args: ("scm_to_stringn" "cannot convert narrow string to output locale" 22 #f #f)Aborted (core dumped)

I've tried rebuilding it with both Guile 2.2 and Guile 3 (running an autoreconf to detect it correctly), both results in the same error. scm_to_stringn is part of the Guile headers, and a backtrace points to the same culprint:

Quote:

0x00007ffff7894a5b in pthread_kill@@GLIBC_2.34 () from /lib64/libc.so.6 (gdb) bt #0 0x00007ffff7894a5b in pthread_kill@@GLIBC_2.34 () from /lib64/libc.so.6 #1 0x00007ffff7840dd2 in raise () from /lib64/libc.so.6 #2 0x00007ffff782649f in abort () from /lib64/libc.so.6 #3 0x00007ffff7db4861 in scm_throw () from /usr/lib64/libguile-3.0.so.1 #4 0x00007ffff7daa58c in ?? () from /usr/lib64/libguile-3.0.so.1 #5 0x00007ffff7dabaa0 in scm_to_stringn () from /usr/lib64/libguile-3.0.so.1 #6 0x00007ffff7d653ff in ?? () from /usr/lib64/libguile-3.0.so.1 #7 0x00007ffff7db3eaf in ?? () from /usr/lib64/libguile-3.0.so.1 #8 0x00007ffff7db4626 in ?? () from /usr/lib64/libguile-3.0.so.1 #9 0x00007ffff7bbe808 in GC_call_with_stack_base () from /usr/lib64/libgc.so.1 #10 0x00007ffff7daea88 in scm_with_guile () from /usr/lib64/libguile-3.0.so.1 #11 0x00007ffff7d516a5 in scm_boot_guile () from /usr/lib64/libguile-3.0.so.1 #12 0x0000000000402559 in ?? () #13 0x00007ffff7827af7 in __libc_start_call_main () from /lib64/libc.so.6

I also tried to change environment LANGs variables, as some people mentioned around this might be a problem with encoding, with no success.

I wonder if someone knows what this might be, it worked fine for several years on Slackware.