How do I tell backbone that the model is not new

I have an object that's also saved in the server and I'm creating a Backbone model from that object.

But when I save the model, it's doing a PUT request, which is not what I want. How to tell Backbone that the data is already in the server without doing a fetch?

Backbone determines the newness of a model by checking if an id is set :

isNew model.isNew()

Has this model been saved to the server yet? If the model does not yet have an id, it is considered to be new.

And when you save a model,

• if it is new, a POST request will be emitted,
• if it is an update (an id has been set), a PUT request will be sent

Backbone Sync documentation

And as noted by @JayC in the comments :

If there's an issue that the id can't literally be id, you can use idAttribute to say which is the "identity" or key field.