lib/texinputs/isabelle.sty

--- a/lib/texinputs/isabelle.sty	Tue Dec 05 15:29:37 2017 +0100
+++ b/lib/texinputs/isabelle.sty	Tue Dec 05 15:55:14 2017 +0100
@@ -250,6 +250,7 @@
 \newcommand{\isafoldtag}[1]%
 {\includecomment{isadelim#1}\excludecomment{isatag#1}\csarg\def{isafold#1}{\isafold{#1}}}
 
+\isakeeptag{document}
 \isakeeptag{theory}
 \isakeeptag{proof}
 \isakeeptag{ML}