X-editable bootstrap loads forever even with 200

X-editable bootstrap loads forever even with 200

I'm using X-editable bootstrap :
http://vitalets.github.io/x-editable/docs.html
The docs said : If value is valid, you should return HTTP status 200 OK.
Element on page will be updated automatically. No response body required.
And my backend was Rails 3.0.20. From controller (on the logs), it shows
it returned : Completed 200 OK in ... ms
But... The x-editable not update the element on the page , what's going on
here ???