Dependency is somehow ignored

I can not build my project anymore, git bisect revealed commit 3997b41e0389bcaea8b198aed548c1983759fdba as the first bad commit.
I've created a reduced testcase (see attachement).
Basically I have a project TestCase with a product InternalLib (the real project has a lot more products). The project is using another project (included via git submodule, similary to how Qbs is included in QtCreator, but that doesn't really matter) called ExternalProject which contains a product also called ExternalProject, on which InternalLib has a dependency. This structure worked till above mentioned commit. Now qbs seems to ignore the dependency completely and as a result the compiler complains about a missing header.