diff -r 41fc655585e4 -r 2cc9bd9a7357 lib/texinputs/isabelle.sty
--- a/lib/texinputs/isabelle.sty	Mon Mar 22 21:24:25 2021 +0000
+++ b/lib/texinputs/isabelle.sty	Tue Mar 23 13:13:31 2021 +0100
@@ -68,9 +68,6 @@
 \DeclareMathSymbol{\bbbX}{\mathord}{bbbfont}{152}
 \DeclareMathSymbol{\bbbY}{\mathord}{bbbfont}{153}
 \DeclareMathSymbol{\bbbZ}{\mathord}{bbbfont}{154}
-\newcommand{\checkbbbfont}{{%
-\setbox\@tempboxa=\hbox{$\bbbA$}%
-\ifdim\wd\@tempboxa=\z@\PackageError{isabelle/pxfonts}{Missing font txmia}{}\fi}}
 
 \newenvironment{isaantiq}{{\isacharat\isacharbraceleft}}{{\isacharbraceright}}