Doing a grep on /usr/local/texlive/2018/texmf-dist/tex/, I see \expanded is used in a couple oberdiek packages, context, and mathspec. I did not try to figure out if the mathspec usage is compatible. It might be worth notifying its author at some point as a courtesy. FWIW ... .. generic/oberdiek/etexcmds.sty:235:\edef\x{\string\expanded}% generic/oberdiek/etexcmds.sty:236:\edef\y{\meaning\expanded}% generic/oberdiek/etexcmds.sty:239: \let\etex@expanded\expanded generic/oberdiek/etexcmds.sty:272: Could not find \string\expanded.\MessageBreak generic/oberdiek/etexcmds.sty:275: that some package has redefined \string\expanded.% generic/oberdiek/hobsub-generic.sty:3641:\edef\x{\string\expanded}% generic/oberdiek/hobsub-generic.sty:3642:\edef\y{\meaning\expanded}% generic/oberdiek/hobsub-generic.sty:3645:\let\etex@expanded\expanded generic/oberdiek/hobsub-generic.sty:3678: Could not find \string\expanded.\MessageBreak generic/oberdiek/hobsub-generic.sty:3681: that some package has redefined \string\expanded.% .. xelatex/mathspec/mathspec.sty:129:\providecommand\expanded[1]{\edef\@tempa{#1}\@tempa} xelatex/mathspec/mathspec.sty:132: \expanded{\noexpand\setkeys*[eu]{#2}{\expandonce#3\@empty}}} xelatex/mathspec/mathspec.sty:134: \expanded{\noexpand\zf@fontspec{\expandonce#1\@empty}{\expandonce#2\@empty}}} .. Grep finished at Tue May 15 10:18:14