diff --git a/libqpdf/qpdf/rijndael.h b/libqpdf/qpdf/rijndael.h
index a9cd71da..8b4c88f6 100644
--- a/libqpdf/qpdf/rijndael.h
+++ b/libqpdf/qpdf/rijndael.h
@@ -1,5 +1,5 @@
-#ifndef H__RIJNDAEL
-#define H__RIJNDAEL
+#ifndef RIJNDAEL_H
+#define RIJNDAEL_H
 
 #include <qpdf/qpdf-config.h>
 #ifdef HAVE_INTTYPES_H