Good afternoon, the recent version change of expl3 from [2017/04/01] (last TL-16 state) to [2017/05/13] (initial TL-17 state) changed the behaviour of \hbox_s:Nn, which made a hot-fix necessary for one of my packages (ocgx2) on CTAN. The problem boils down to the following code, which used to work with expl3 as of v. 2017/04/01, but fails now with `! Missing } inserted.' error. \documentclass{article} \usepackage{hyperref} \usepackage{expl3} \ExplSyntaxOn \begin{document} \href{https://www.ctan.org}{\dots \hbox_set:Nn0\bgroup CTAN % broken since expl3 [2017/05/13] % \setbox0=\hbox\bgroup CTAN % hot-fix \egroup\box_use:N0 \dots} \end{document} I would like to return to using \hbox_set:Nn instead of \setbox. Alexander