Hi, The new ejson module doesn't support older versions of Erlang because the expected result from the module's on_load fun changed from true to ok. The attached one-line change (as a git diff) fixes it for me using the standard Erlang packages on Ubuntu 10.10 and 11.04 but I don't have a newer version of Erlang installed to test against. Obviously, with this change applied I'm still using the non-NIF json implementation but at least the ejson module loads ;-). - Matt