`monocraft.py --output-ttc` segfaults

Running monocraft.py for me with --output-ttc results in the following output:

>python ./monocraft.py --output-ttc
Added 258 diacritic combinations
Generated 1483 characters
fish: Job 1, 'python ./monocraft.py --output-…' terminated by signal SIGSEGV (Address boundary error)

I am running python 3.14.3 with the fontforge python package version 20251009 on unstable nixpkgs. I tried it with python 3.13.12 and the same issue occurs. Everything seems to work fine otherwise.