export from org-mode broken

http://stackoverflow.com/questions/22565379/emacs-org-mode-python-source-blocks-dont-export-with-python-mode-el

I recently configured my Emacs setup to use python-mode.el instead of python.el. This changed has apparently caused org mode to no longer be able to export python source blocks, as I get
org-export-format-source-code-or-example: "End of buffer"

as the only message after export, and no export file is generated.

I'd like to know why this is, and what I can do to fix it. My python-mode.el is installed through el-get (not that I think that is important). It is loaded in my init file like so:
(add-to-list 'load-path "~/.emacs.d/el-get/python-mode/")
(autoload 'python-mode "python-mode" "Python Mode." t)
(add-to-list 'auto-mode-alist '("\\.py\\'" . python-mode))
(add-to-list 'interpreter-mode-alist '("python" . python-mode))