Eclipse "go to definition" problem

I'm using PyDev for eclipse and am experiencing some issues with "go to definition". It works for most modules, but for some site packages it does not. It does the "bump" sound and then nothing happens. One of the packages that doesn't work is Twisted, which is weird since the source is included and right there. Any idea how to fix this?

The go to definition works just fine. The problem was that eclipse didn't know where to find the source. You can go to window > preferences > pydev > interpreter > New folder, and add the folders missing. Even though you've added site-packages to the configuration, you still have to add subfolders separately to get code assist and to be able to go to the definition.