diff --git a/doc/guide/preamble.sdf b/doc/guide/preamble.sdf
index 9ee98ffac2..93fb3d5b9c 100644
--- a/doc/guide/preamble.sdf
+++ b/doc/guide/preamble.sdf
@@ -91,7 +91,7 @@ ________________<BR>
 <P>
 <FONT COLOR="#808080" FACE="Arial,Verdana,Helvetica" SIZE="1"><B>
 ________________<BR>
-<SMALL>&copy; Copyright 2011, <A HREF="https://www.OpenLDAP.org/foundation/">OpenLDAP Foundation</A>, <A HREF="mailto:info@OpenLDAP.org">info@OpenLDAP.org</A></SMALL></B></FONT>
+<SMALL>&copy; Copyright 2011-2021, <A HREF="https://www.OpenLDAP.org/foundation/">OpenLDAP Foundation</A>, <A HREF="mailto:info@OpenLDAP.org">info@OpenLDAP.org</A></SMALL></B></FONT>
 
 	!endblock
 !endmacro