diff -r 533df6cedc2d -r f23bee3c0682 lib/texinputs/isabelle.sty
--- a/lib/texinputs/isabelle.sty	Mon Aug 28 20:28:44 2000 +0200
+++ b/lib/texinputs/isabelle.sty	Mon Aug 28 20:29:19 2000 +0200
@@ -16,10 +16,14 @@
 
 \newdimen\isa@parindent\newdimen\isa@parskip
 
-\newenvironment{isabelle}{%
-\trivlist\isa@parindent\parindent\parindent0pt%
+\newenvironment{isabellebody}{%
+\isa@parindent\parindent\parindent0pt%
 \isa@parskip\parskip\parskip0pt%
-\isastyle\item\relax}{\endtrivlist}
+\isastyle}{}
+
+\newenvironment{isabelle}
+{\begin{isabellebody}\begin{trivlist}\item\relax}
+{\end{trivlist}\end{isabellebody}}
 
 \newcommand{\isa}[1]{\emph{\isastyleminor #1}}