--- a/lib/texinputs/isabellesym.sty Thu Mar 14 21:17:40 2019 +0100
+++ b/lib/texinputs/isabellesym.sty Fri Mar 15 22:02:05 2019 +0100
@@ -367,6 +367,7 @@
\newcommand{\isasymcomment}{\isatext{\isastylecmt---}}
\newcommand{\isasymproof}{\isamath{\,\langle\mathit{proof}\rangle}}
+\newcommand{\isactrlmarker}{\isatext{\ding{48}}} %requires pifont
\newcommand{\isactrlassert}{\isakeywordcontrol{assert}}
\newcommand{\isactrlcancel}{\isakeywordcontrol{cancel}}
\newcommand{\isactrlbinding}{\isakeywordcontrol{binding}}