Problem with reactor when using attached goal

Here's my project dir structure:

trunk/
  |_ core/
    |_ api/
      |_ (several projects here)
    |_ uberjar/ (assembly project)
  |_ samples
    |_ testdata
      |_ empty-jar
      |_ (...)

If I build the trunk/core/ubjerjar project alone it works fine. Note: I have attached the "attached" goal to the verify phase so the assembly can be created when calling "mvn install".

If I build the project from the trunk by typing "mvn install", the uberjar/ project fails saying that the empty-jar artifact cannot be found in the local repository. That's normal it cannot be found because there are no dependencies on it in the core/ branch and it hasn't been built yet when the uberjar project executes. Of course there are no dependencies to it in the uberjar project.

It seems there's something fishy happening in the assembly plugin implementation...

Thanks