How to access options when extending a leaflet class?

Question

I am trying to extend a Leaflet class, and looking at the documentation it gives this example:

var MyBoxClass = L.Class.extend({

    options: {
        width: 1,
        height: 1
    },

    initialize: function(name, options) {
        this.name = name;
        L.setOptions(this, options);
    }
    
});

var instance = new MyBoxClass('Red', {width: 10});

console.log(instance.name); // Outputs "Red"
console.log(instance.options.width); // Outputs "10"
console.log(instance.options.height); // Outputs "1", the default

However, if I try to access this.options.height in initialize after calling L.setOptions it is undefined. Instead there appears to be a this.options.prototype.height.

How should I be accessing options members so I get the default if the caller doesn't define a value?

Thanks