idProperty problem with store defined by viewModel

Hi. I have idProperty problem with store defined by viewModel, it's always equal 'id'

Code:

Ext.define('App.model.Role', {
    extend: 'Ext.data.Model',
    idProperty: 'RoleID',
    fields: [{
        name: 'RoleID',
        type: 'int'
    },{
        name: 'RoleName',
        type: 'string'
    }]
});

Code:

Ext.define('App.view.RoleModel', {
    extend: 'Ext.app.ViewModel',
    alias: 'viewmodel.rolemodel',
    stores: {
        roles: {
            model: 'App.model.Role',
            autoLoad: true
        }
    }
});

When I bind viewModel to the GridPanel, records in the store have idProperty equal 'id'.

Can anybody help?

P.S.: Sorry for my english...