Thread:Extension talk:Push/Problems pushing embedded files

When I tick the Include embedded files option, I get the following error shown in the Chrome Dev Console:

GET http://localhost:8888/wiki/api.php?action=pushimages&format=json&images=File%3AMold+and+sterile.jpg&targets=http%3A%2F%2Fw.thgie.ch 500 (Internal Server Error) load.php?debug=false&lang=en&modules=jquery%2Cmediawiki&only=scripts&skin=vector&version=20131206T2…:128

Pushing just the page content works fine. I'm using the MAMP app on OSX 10.9 which has cURL installed. phpinfo tells me cURL is enabled and version 7.28.1.

Any idea what I could do to resolve this issue?