Multi-project site navigation suddenly broken

Not exactly sure when this started, but the generated site navigation for my multiproject site is broken; sub-modules now use the same navigation links as the master project ... thus per-module files are inaccessible and many links are broken.,

See http://tapestry.formos.com/nightly/tapestry5 for an example.

Using maven-site-plugin verson 2.0-beta-6.

It seems to work correctly if I downgrade to 2.0-beta-5.