Calling isValid() on a Model throws an error in Modern Production build

[cesidio]

//The Model
Ext.define(MyApp.model.UserLogin', {
    extend: 'Ext.data.Model',
    requires: [],

    fields: [
        {name: 'userId', type: 'string'},
        {name: 'password', type: 'string'}
    ],
    validators: {
        userId: [
            {type: 'email', message: "Wrong Email Format"},
            {type: 'presence'}
        ],
        password: [
            {type: 'length', min: 4},
            {type: 'presence'}
        ]
    },
    proxy: {
      ...
    }
});

//In the app
var user = Ext.create('MyApp.model.UserLogin', {
            userId: fields.user,
            password: fields.password
        });


        if (user.isValid()) { *****      
            ...
        }
        else {
            ...
        }

***** This line throws "Uncaught TypeError: c is not a function"

I made sure that userId and password had valid values.

[cesidio]

Solution found:

It seems that I have to require ['Ext.data.validator.Email', 'Ext.data.validator.Presence', 'Ext.data.validator.Length'] when using the testing/production builds.