diff --git a/lectures/lecturecommon.sty b/lectures/lecturecommon.sty
index 8c614b9..62e37ee 100644
--- a/lectures/lecturecommon.sty
+++ b/lectures/lecturecommon.sty
@@ -154,8 +154,6 @@
 
 % Class number.
 \newcounter{chapterplusone}
-\setcounter{chapterplusone}{\value{chapter}}
-\stepcounter{chapterplusone}
 \newcommand{\ClassNumber}{\thechapter}
 \newcommand{\ClassNumberPlusOne}{\thechapterplusone}
 \newcommand{\SetClassNumber}[1]{%