diff --git a/swift/obj/updater.py b/swift/obj/updater.py
index 57752f4e33..8b77001ba4 100644
--- a/swift/obj/updater.py
+++ b/swift/obj/updater.py
@@ -233,6 +233,16 @@ class OldestAsyncPendingTracker:
         self.ac_to_timestamp = {}
 
     def add_update(self, account, container, timestamp):
+        """
+        Add or update a timestamp for a given account and container.
+
+        :param account: (str) The account name.
+        :param container: (str) The container name.
+        :param timestamp: (float) The timestamp to add or update.
+        """
+        # Ensure the timestamp is a float
+        timestamp = float(timestamp)
+
         ac = (account, container)
 
         if ac in self.ac_to_timestamp:
@@ -273,7 +283,7 @@ class OldestAsyncPendingTracker:
 
     def get_oldest_timestamp(self):
         if self.sorted_entries:
-            return float(self.sorted_entries[0][0])
+            return self.sorted_entries[0][0]
         return None
 
     def get_oldest_timestamp_age(self):
diff --git a/test/probe/test_object_async_update.py b/test/probe/test_object_async_update.py
index 1e87c4d4f7..f7276cc25d 100644
--- a/test/probe/test_object_async_update.py
+++ b/test/probe/test_object_async_update.py
@@ -403,6 +403,7 @@ class TestObjectUpdaterStats(ReplProbeTest):
                 container = entry['container']
                 timestamp = entry['timestamp']
                 self.assertIsNotNone(timestamp)
+                self.assertIsInstance(timestamp, float)
                 ac_set.add((account, container))
 
         for ac in ac_set: