Derived json with null property value

I am constructing a json object, and I want all properties to exist, even if the source value was null.  Is this possible, or am I simply going about it incorrectly?

Here is my data mapping expression:

@(address1=byName('Address1'),
    address2=byName('Address2'),
    city=byName('City'),
    state=byName('State'),
    zip=byName('Zip'))

Here is the output:

{
    "address1": "123 Any Street",
    "city": "Smalltown",
    "state": "WA",
    "zip": "12345"
}

Here is the desired output:

{
    "address1": "123 Any Street",
    "address2": null,
    "city": "Smalltown",
    "state": "WA",
    "zip": "12345"
}