This is for Jeremy’s(bitsweat) attention.
As Gabe pointed out in the comments, “This patch introduced a regression my app’s tests because our activeresource mocks did not set a content-type header. This was easy enough to fix once I debugged it, but it was pretty nasty to track down since the result is simply that the error messages are ignored and save returns true and the object appears valid with no trace of what happened without debugging deep into ActiveResource. Even though in production this case ought to never happen, in tests it’s the default with no indication that you would need to set a Content-Type header.”
Thanks Jatinder http://blog.jatinder.me