Backbone create sends PUT /api/presets/undefined instead of POST /api/presets

I'm porting code written for Backbone 1.0.0 to a new app using Backbone 1.1.2 and I noticed that isNew() seems broken for objects using custom idAttributes.

We are using model.save(settings, {wait:true}) and the Model is configured with idAttribute: "name" :

Backbone 1.1.2 wrongfully sends the request to PUT /api/presets/undefined.
Before it was going to POST /api/presets/.

Our device's presets map to filenames in a directory and they don't have ID the web interfaces uses the name as ID for this model.

In Backbone 1.0.0, the same code was causing isNew() to return true:

This is our save() call. I inspected that the model does not have name in it's attributes and is passed a new one via settings:

This could be the commit that broke this :

https://github.com/jashkenas/backbone/commit/11cc0e863f9951b4242144d65b581348bd9ee092

I tried to patch this commit but it does not resolves it:

https://github.com/jashkenas/backbone/commit/9f81d980f0599e8691af80034944d4abafb3f44b

So I continue investigating why isNew() walks on an object that has "name" set in the model and it is because of this line and that wait is true :