diff -r d36864e3f06c -r a0d49ed5a23a doc-src/Codegen/style.sty
--- a/doc-src/Codegen/style.sty	Fri Sep 24 14:03:44 2010 +0200
+++ b/doc-src/Codegen/style.sty	Fri Sep 24 14:56:16 2010 +0200
@@ -28,10 +28,14 @@
 \newcommand{\quotebreak}{\\[1.2ex]}
 
 %% typewriter text
-\newenvironment{typewriter}{\renewcommand{\isadigit}[1]{{##1}}%
+\isakeeptag{typewriter}
+\newenvironment{typewriter}{\renewcommand{\isastyletext}{}%
+\renewcommand{\isadigit}[1]{{##1}}%
 \parindent0pt%
 \isabellestyle{tt}\isastyle%
 \fontsize{9pt}{9pt}\selectfont}{}
+\renewcommand{\isatagtypewriter}{\begin{typewriter}}
+\renewcommand{\endisatagtypewriter}{\end{typewriter}}
 
 \isakeeptag{quotett}
 \renewcommand{\isatagquotett}{\begin{quote}\isabellestyle{tt}\isastyle}