Meteor: Use value from an autoValue field to compute for value in another autoValue field

Question

Meteor v 1.10.1. I am using meteor-collection2@3.0.6 and using simpl-schema v1.5.7 (NPM package)

I have this schema:

import SimpleSchema from "simpl-schema";

Orders.schema = new SimpleSchema ({
  name: {
    type: String
  },
  items: {
    type: Array
  },
  "items.$": {
     type: Object,
     Blackbox: true
  },

  orderTax: {
    type: Number,
    optional: true,
    autoValue: function () {
      if(this.isInsert || this.isUpdate) {
        return 0.5
     }
  }
  total: {
    type: Number,
    optional: true,
    autoValue: function () {
      if(this.isInsert || this.isUpdate) {
        const tax = this.field('orderTax').value;
        // Here tax is undefined
     }
    } 

})

orderTax is not sent as part of the object for simple-schema clean(), and yes that is the expected behavior, orderTax should only be computed for by the autoValue function on orderTax.

How do I use the autoValue computed from orderTax in total autoValue computation?

This setup works with earlier version of collection2 and earlier version aldeed:simple-schema (not NPM package)