An update: in Python 2.7 through 3.3, fixing this should only affect http.client/httplib, because they do most of their header parsing themselves. Fixing this in later versions of Python is more interesting, as http.client got rewritten to use email.parser (which uses email.feedparser). This means any change to fix this problem in HTTP will also affect anything else that uses this module. Not sure how problematic that is yet.