IonStruct object does not match instanceof dom.Value when used inside JSON stringify replacer

index.js

const { load, dom }  = require('ion-js');

const ionStruct = load(`$ion_1_0
{
  foo:"bar"
}`);

const ionList = load(`$ion_1_0
[
  "hello",
  "world"
]`);

console.log(ionStruct instanceof dom.Value); // returns true
console.log(ionStruct['foo'] instanceof dom.Value); // returns true
console.log(ionList instanceof dom.Value); // returns true
console.log(ionList[0] instanceof dom.Value); // returns true
console.log(ionList[1] instanceof dom.Value); // returns true

// So far, it all looks good.

const replacer = (key, value) => {
    if (value instanceof dom.Value) {
        console.log('instance of dom.Value:', value);
    } else {
        console.log('not instance of dom.Value:', value, 'Actual type:', typeof value);
    }
    return value;
}

const jsonObject = {
    ionStruct: ionStruct,
    ionList: ionList,
}

JSON.stringify(jsonObject, replacer, 2);

// Output:

`
true
true
true
true
true
not instance of dom.Value: {
    ionStruct: Struct { _fields: [Object: null prototype] { foo: [Array] } },
    ionList: List(2) [ [String: 'hello'], [String: 'world'] ]
} Actual type: object
not instance of dom.Value: [Object: null prototype] { foo: [String: 'bar'] } Actual type: object
instance of dom.Value: [String: 'bar']
instance of dom.Value: List(2) [ [String: 'hello'], [String: 'world'] ]
instance of dom.Value: [String: 'hello']
instance of dom.Value: [String: 'world']
`

Line 50 expected (because line 41 returns true):

instance of dom.Value: ...

Line 50 actual:

not instance of dom.Value: ...