Catalog zone Notifies for child zones

[G H]

I have a master and a slave server setup with functional catalog zone transfers. Upon initial daemon start, the slave will pull the catalog zone, and then pull the domain zones contained within said catalog zone (let's refer to these domains as child domains).

If I modify the serial on the master's catalog zone file and restart, the slave will successfully receive a NOTIFY and pull down the latest catalog zone file contents.

However, if I modify the serial of child domain zone, no NOTIFY is ever sent. The only way I can get the slave server to pull down the latest contents of the child domain zone is to delete the /var/cache/bind contents and restart the slave daemon. What is the correct method of letting slave servers know that the child domain zones are changed? I really want to avoid putting an "also-notify" in the definition for child zone on the master.