diff --git a/sharded_queue/__init__.py b/sharded_queue/__init__.py
index 804d85c..1dbe040 100644
--- a/sharded_queue/__init__.py
+++ b/sharded_queue/__init__.py
@@ -285,7 +285,7 @@ def calculate_timestamp(cls, delta: float | int | timedelta) -> float:
 
         timestamp: float = now.timestamp()
         if not isinstance(delta, timedelta):
-            timestamp = delta = delta
+            timestamp = timestamp + delta
 
         return timestamp
 
diff --git a/tests/test_recurrent.py b/tests/test_recurrent.py
index 3155dc9..b9832c6 100644
--- a/tests/test_recurrent.py
+++ b/tests/test_recurrent.py
@@ -45,10 +45,15 @@ async def stats() -> tuple[int, int, int]:
     )
     assert await stats() == (0, 1, 0), 'recurrent pipe contains request'
 
+    deffered_registration = datetime.now().timestamp()
     await Worker(lock, queue).loop(1)
     assert await stats() == (1, 1, 0), 'added defered request'
     assert await lock.exists(recurrent_pipe)
 
+    [deferred] = await queue.storage.range(deferred_pipe, 1)
+    request = queue.serializer.deserialize(DeferredRequest, deferred)
+    assert request.timestamp >= deffered_registration
+
     await lock.release(recurrent_pipe)
     await Worker(lock, queue).loop(1, handler=RecurrentHandler)
     assert await stats() == (1, 1, 0), 'no deffered duplicates'