diff --git a/lib/src/utils/device_keys_list.dart b/lib/src/utils/device_keys_list.dart
index f350032..4304a2f 100644
--- a/lib/src/utils/device_keys_list.dart
+++ b/lib/src/utils/device_keys_list.dart
@@ -20,7 +20,7 @@ class DeviceKeysList {
   Map<String, dynamic> toJson() {
     final Map<String, dynamic> data = Map<String, dynamic>();
     data['user_id'] = this.userId;
-    data['outdated'] = this.outdated;
+    data['outdated'] = this.outdated ?? true;
 
     Map<String, dynamic> rawDeviceKeys = {};
     for (final deviceKeyEntry in this.deviceKeys.entries) {