SwiftData Lightweight Migraton failed with VersionedSchema

Setup

I am running a versionedSchema for my SwiftData model and attempting a migration. The new version contains a new attribute, with a type of a new custom enum defined in the @Model class, a default value, and a private(set). Migration was completed with a migrationPlan with nil values for willMigrate and didMigrate.

Example - Previous Version

@Model
class MyNumber {
    var num: Int
 
    init() {
        // Init Code
    }
}

Example - Newest Version

@Model
class MyNumber {
    var num: Int
    private(set) var rounding: RoundAmount = MyNumber.RoundAmount.thirtyMinute 
 
    init() {
        // Init Code
    }
 
    enum RoundAmount {
        case fiveMinute, tenMinute, thirtyMinute
    }
}

Issue

Running this code, I get a swiftData error for “SwiftData/ModelCoders.swift:1585: nil value passed for a non-optional keyPath, /MyNumber.rounding”

I assume this means a failure of the swiftData lightweight migration? I have reverted the version, removed private(set) and re-tried the migration with no success.

Using the versionedSchema with migrationPlans, are lightweight migrations possible? Could this be an issue with the use of a custom enum? Other changes in my actual project migrated successfully so I’m lost on why I’m having this issue.