Can't get PsiDocumentManager.commitDocument to update PSI

I'm listening to document changes in the fileContentLoaded method of a FileDocumentManagerListener.

This works just fine, but the action i want to perform also depends on the PSI representation so i would think that doing PsiDocumentManager.commitDocument(changedDocument) would update the PSI representation of the changed class. As it turns out it doesn't.....

Any idea how i can do this or to why commitDocument isn't updating the PSI representation ?

Thanks...