Use of #include in APT page causes NullPointerException during page rendering

In the last 2 days I tried to get this thing working.
The situation is the following: I'm working on a maven site project and, for some pages, I'm currently using the APT format.
I'd really like to be able to include existing APT pages inside an APT page, in order to make the collaboration between the 4 members of the project much easier and smoother.
To give an idea, I'd like to do this:
merged-page.apt:

  ---
  Title
  ---
  ---
  ---

  Develeper 1 proposal:

  <include page 1>

  Developer 2 proposal:

  <include page 2>

  etc.

At first, I tried using the %snippet DOXIA macro, but the included APT page would not be rendered to HTML even setting verbatim=false.
Then, I tried the #include macro from Velocity. I renamed my APT file to filename.apt.vm in order to trigger the Velocity processor on it and put the #include line in the file, but, whenever I launch maven site I keep getting this error:

and the page is not generated.
Is there a way to fix this?