Hi, there is a segfault produced by LuaTeX, Version 1.12.0 (TeX Live 2020/Debian) when processing the following: \ifdefined\directlua \protected\def\pdfmapfile {\pdfextension mapfile } \protected\def\pdfmapline {\pdfextension mapline } \edef\pdfgentounicode {\pdfvariable gentounicode} \protected\def\pdfglyphtounicode {\pdfextension glyphtounicode } \fi \pdfglyphtounicode{A}{0041} \pdfgentounicode=1 \pdfmapfile{} \pdfmapline{cmr10 CMR10 34} % no font embedding anything \end PdfTex, Version 3.14159265-2.6-1.40.21 (TeX Live 2020/Debian) gives the following assertion: pdftex: ../../../texk/web2c/pdftexdir/writefont.c:555: write_fontdictionary: Assertion `fo->fd->builtin_glyph_names != NULL' failed. Aborted If the combination of using \pdfgentounicode and not embedding any font is invalid, some reasonable error message should be produced. Best regards Martin