I'm using backbone for a reasonably complicated form. I have a number of nested models, and have been computing other variables in the parent model like so:

// INSIDE PARENT MODEL

computedValue: function () {
    var value = this.get('childModel').get('childModelProperty');
    return value;
}

This seems to work fine for keeping my UI in sync, but as soon as I call

.save()

on the parent model, I get:

Uncaught TypeError: Object #<Object> has no method 'get' 

It seems that the child model kind of temporarily stops responding.

Am I doing something inherently wrong?

EDIT: The stack trace is:

Uncaught TypeError: Object #<Object> has no method 'get' publish.js:90
Backbone.Model.extend.neutralDivisionComputer publish.js:90
Backbone.Model.extend.setNeutralComputed publish.js:39
Backbone.Events.trigger backbone.js:163
_.extend.change backbone.js:473
_.extend.set backbone.js:314
_.extend.save.options.success backbone.js:385
f.Callbacks.o jquery.min.js:2
f.Callbacks.p.fireWith jquery.min.js:2
w jquery.min.js:4
f.support.ajax.f.ajaxTransport.send.d