emberjs/ember.js — pull request #1130 by trek (2012-07-08 16:52:52+00:00)
Title: Use Ember.set when cloning keywords

For cases where keywords becomes watched and Object.defineProperty is unavailable. Resolves #1062.

I imagine a similar fix should be pulled into 0.9 stable, although given the shaky state of Router on that branch, I'll wait for comment.