To answer eli.bendersky's questions: 1. That's just the name of the file with my changes in it. I pulled the original file from Hg, copied it to "ElementTree_new.py", made my changes, and created a patch from the two. 2. I'm not very familiar with the structure of the codebase for Python, so I'll provide some information that sounds relevant to me... The changes I made were for the ElementTree.py file under cpython/Lib/xml/etree/ . I used http://hg.python.org/cpython/file/54055646fd1f/Lib/xml/etree/ElementTree.py as the base to make a new patch, reflecting storchaka's recommendation on logic order and a clarification on path name for the modified file. The source for the 'ElementC14N' module is not part of Python, so I cannot modify the code for the '_serialize_c14n' function. It appears that this is dependent on http://bugs.python.org/issue13611 . Looks like I may need to refactor this patch to work in a way that does not alter the signature for the _serialize_* methods.