diff --git a/include/hpdf.h b/include/hpdf.h
index 1cf0dd9..cce9b59 100644
--- a/include/hpdf.h
+++ b/include/hpdf.h
@@ -54,6 +54,7 @@
 #include "hpdf_types.h"
 
 typedef void         *HPDF_HANDLE;
+typedef HPDF_HANDLE   HPDF_Boolean;
 typedef HPDF_HANDLE   HPDF_Doc;
 typedef HPDF_HANDLE   HPDF_Page;
 typedef HPDF_HANDLE   HPDF_Pages;
