diff --git a/src/actors/runtime/AbstractActor.ts b/src/actors/runtime/AbstractActor.ts
index 22eaac25..c8175d8e 100644
--- a/src/actors/runtime/AbstractActor.ts
+++ b/src/actors/runtime/AbstractActor.ts
@@ -95,15 +95,15 @@ export default abstract class AbstractActor {
   async registerActorReminder<_Type>(
     reminderName: string,
     dueTime: Temporal.Duration,
-    period?: Temporal.Duration,
-    ttl?: Temporal.Duration,
+    period?: Temporal.Duration|undefined,
+    ttl?: Temporal.Duration|undefined,
     state?: any,
   ) {
     await this.actorClient.actor.registerActorReminder(this.actorType, this.id, reminderName, {
       period,
       dueTime,
-      data: state,
       ttl,
+      data: state,
     });
   }