Starting KVM guest after memory change

After a memory module was taken out the system, the KVM guest was failing to start complaining about insufficient memory. Editing the domain XML file (in /etc/libvirt/qemu on Debian) to use less RAM and then trying to start the guest did not work.

I had to do this:
libvirt-bin restart

for the the updated XML file to be read and for the guest to start.