diff -r 72188cd6bbfc -r 9c5edbf5eefd lib/texinputs/isabelle.sty
--- a/lib/texinputs/isabelle.sty	Fri Mar 17 22:52:29 2000 +0100
+++ b/lib/texinputs/isabelle.sty	Fri Mar 17 22:53:19 2000 +0100
@@ -11,8 +11,8 @@
 \newcommand{\isabellestyle}{}
 \newenvironment{isabelle}{%
 \newdimen\@parindent\@parindent\parindent\parindent0pt%
-\newdimen\@parskip\@parskip\parskip\parskip0.5ex%
-\small\tt\slshape\isabellestyle\mbox{}}{}
+\newdimen\@parskip\@parskip\parskip\parskip0pt%
+\small\tt\slshape\isabellestyle}{}
 \newcommand{\isanewline}{\mbox{}\\\mbox{}}
 
 \chardef\isabraceleft=`\{