In order for this to work, you must run the following commands after you update your pacakges.

dpkg-scansources dists/14.04/source/source /dev/null | gzip -9c > dists/14.04/source/source/Packages.gz
dpkg-scanpackages dists/14.04/binary/binary-i386 /dev/null | gzip -9c > dists/14.04/binary/binary-i386/Packages.gz
dpkg-scanpackages dists/14.04/binary/binary-amd64 /dev/null | gzip -9c > dists/14.04/binary/binary-amd64/Packages.gz