diff --git a/brq/operator.py b/brq/operator.py
index 8a79311..99a502a 100644
--- a/brq/operator.py
+++ b/brq/operator.py
@@ -72,7 +72,7 @@ async def get_defer_timestamp_ms(
         defer_hours: int = 0,
         defer_minutes: int = 0,
         defer_seconds: int = 0,
-    ):
+    ) -> int | None:
         if not any(
             [
                 defer_until,