If you check the build logs, you can see: checking for vapigen... /usr/bin/vapigen
and later: Vala support: yes Also if you do a search for dh_missing, you can see what files are not being installed. As far as I can tell, there are no vapi files anywhere and there is not an obvious thing wrong in the packaging. https://buildd.debian.org/status/package.php?p=gegl (Click Installed to see the build log) Thanks, Jeremy Bicha