diff --git a/tex/booknotes.cls b/tex/booknotes.cls
index 48406e9..00e3d4c 100644
--- a/tex/booknotes.cls
+++ b/tex/booknotes.cls
@@ -344,5 +344,7 @@
     \import{./figures/}{#1.pdf_tex}
 }
 
+\def\@section{}
+
 \makeatother
 
diff --git a/tex/notes.cls b/tex/notes.cls
index 0f1096b..f0badae 100644
--- a/tex/notes.cls
+++ b/tex/notes.cls
@@ -320,8 +320,8 @@
     \subsubsection{#1}
 }
 
-\newcommand{\chapter}[1]{
-    \section{#1}
+\newcommand{\chapter}[2][O]{
+    \section{#2}
 }
 \renewcommand{\part}[1]{}