Required field - Realm Kotlin SDK

So here’s the thing. I have troubles with an array/realmList type. I want to define a required field for the array/RealmList type. I’ve defined a required “array” field in my Mongo Atlas schema. And I’ve set a default value for that same field in the RealmObject model class. But whenever I try to launch an android app, I’ve been getting this same error in the logs:

ending session with error: failed to add app schema for ns=‘mongodb-atlas.diaries.Diary’ for new top-level schema “Diary”: sync-incompatible app schema for the same collection already exists. This app schema is incompatible with error: “array property “imagess” must be optional to be sync-compatible”. To continue, delete the app schema in Atlas App Services, or update it to match the app schema defined on the device (ProtocolErrorCode=225)

This is my schema:

  "title": "Diary",
  "bsonType": "object",
  "required": [
  "properties": {
    "_id": {
      "bsonType": "objectId"
    "ownerId": {
      "bsonType": "string"
    "mood": {
      "bsonType": "string"
    "title": {
      "bsonType": "string"
    "description": {
      "bsonType": "string"
    "images": {
      "bsonType": "string"
    "imagess": {
      "bsonType": "array",
      "items": {
        "bsonType": "string"
    "date": {
      "bsonType": "date"

This is my model class:

open class Diary constructor(
    var _id: ObjectId,
    var ownerId: String,
    var mood: String,
    var title: String,
    var description: String,
    var images: String,
    var imagess: RealmList<String>,
    var date: RealmInstant,
) : RealmObject {
    constructor() : this(
        _id = ObjectId.create(),
        ownerId = "",
        mood =,
        title = "",
        description = "",
        images = "",
        imagess = realmListOf("stev", "stev2"),
        date = RealmInstant.from(System.currentTimeMillis(), 0),