In certain configurations, Py++ won't create the source files that contain the Boost.Python registrations. The build will complete "successfully" and it's not until you attempt to use the extension that you find out declarations are missing. I'm attaching an example that contains a Py++ script with two module builders that exhibit this problem. The first builds a fake header as string and the second uses a real header file bundled with the example. The second is commented out.