diff --git a/lectures/otagoslides.cls b/lectures/otagoslides.cls
index 687e856..c8eda58 100644
--- a/lectures/otagoslides.cls
+++ b/lectures/otagoslides.cls
@@ -6,13 +6,14 @@
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %
 % Version History
-% v1.0   Initial version, rebuilt from deprecated lectureslides class.
+% v1.0    Initial version, rebuilt from deprecated lectureslides class.
+% v1.0.1  Stopped hyperref complaining about invalid tokens in PDF metadata.
 %
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
 \NeedsTeXFormat{LaTeX2e}[2001/06/01]
 \ProvidesClass{otagoslides}%
-         [2021/02/23 Otago lecture slides style, v.1.0]
+         [2023/01/26 Otago lecture slides style, v.1.0.1]
 
 
 % "Stream of conciousness" chapters vs. explicit individual classes. NOTE:
@@ -172,6 +173,13 @@
     }%
 }
 
+% Disable certain commands in PDF metadata to stop hyperref complaining
+% about invalid tokens. This is caused by \insertchapternumber in the
+% Otago Beamer theme, which calls \usebeamerfont and \usebeamercolor.
+\pdfstringdefDisableCommands{%
+    \def\usebeamercolor#1{}%
+    \def\usebeamerfont#1{}%
+}
 
 % Document setup.
 \author{}