Attempted to handle event `willCommit` on while in state root.loaded.updated.inFlight

Attempted to handle event `willCommit` on while in state
root.loaded.updated.inFlight

I'm learning how to use EmberJS by doing the introductory tutorial form
the "Getting started" page. However, when I get to the "Accepting edits"
part, I have a bug:
Uncaught Error: Attempted to handle event `willCommit` on
<Todos.Todo:ember304:3> while in state root.loaded.updated.inFlight.
The call to Todos.TodoController.acceptChanges() seems to be triggering
that error. The part I'm referring about is this one:
http://emberjs.com/guides/getting-started/accepting-edits/
After reading up on model lifecycle in Ember -
http://emberjs.com/guides/models/model-lifecycle/#toc_in-flight - I still
don't get why this bug appears.
One work-around is to save the model each time it changes (so every time
the value of the <input> changes. Which works fine but would probably
perform poorly with a HTTP API (as opposed to fixtures).
Could this be due to BC breaking changes in the ember-data lib? What else
could cause this?



Versions of libraries I've used:
jQuery: 2.0.3
Handlebars 1.0.0
EmberJS: 1.0.0 RC7
Ember Data: v0.13-102-g6bdebe7