I'm using Heroku with Django and using Piston for API stuff. 

We migrated from plain Amazon EC2 to Heroku. Everything works (every aspect of the website) except for some of the API calls.

When I run an API call to get a list of objects (trees) that user has, I get the following:

```
RuntimeError at /api/tree.json
maximum recursion depth exceeded while calling a Python object

```

Anyone have any ideas of why this could be?
Thanks in advance, I'd really appreciate any hints/advice!