diff --git a/etc/schema/dbnotn.rnc b/etc/schema/dbnotn.rnc
index 2a6185f27fd..10ecc53b18f 100644
--- a/etc/schema/dbnotn.rnc
+++ b/etc/schema/dbnotn.rnc
@@ -65,6 +65,7 @@ notation.class =
   | "JPEG"
   | "IGES"
   | "PCX"
+  | "PDF"
   | "PIC"
   | "PNG"
   | "PS"