Answering to myself, I was using the wrong functions for pkg_resources, and in theory I should use find_distributions. So I tried the following - construct a very minimal egg with a foolproof module - find and add to the working_set all the distributions found for d in find_distributions('egg_directory'): working_set.add(d) from foolproof import fool And in fact in sys.path the foolproof egg is there, but then I can't still import foolproof... Is there anything else I need to do? Here is what the egg look like.. -rw-r--r-- 47 27-Oct-2011 16:03:16 foolproof.py -rw-r--r-- 291 27-Oct-2011 16:11:44 foolproof.pyc -rw-r--r-- 153 27-Oct-2011 16:11:44 EGG-INFO/SOURCES.txt -rw-r--r-- 1 27-Oct-2011 16:11:44 EGG-INFO/zip-safe -rw-r--r-- 183 27-Oct-2011 16:11:44 EGG-INFO/PKG-INFO -rw-r--r-- 1 27-Oct-2011 16:11:44 EGG-INFO/dependency_links.txt -rw-r--r-- 10 27-Oct-2011 16:11:44 EGG-INFO/top_level.txt