document.ProjectItem.ContainingProject.Object as VCProject yields null in VS2013, works fine in 2012

I'm implementing a DocumentSaved callback. It starts like this:

private void documentSaved(Document document)
{            
   if (document != null && document.Language == "C/C++")   {      VCProject project = document.ProjectItem.ContainingProject.Object as VCProject;   }
}

project variable is always null in VS2013, works fine in 2012. Do I need to adjust something for 2013?