diff --git a/staffeln/objects/queue.py b/staffeln/objects/queue.py
index f1f6458..e709ce1 100644
--- a/staffeln/objects/queue.py
+++ b/staffeln/objects/queue.py
@@ -7,7 +7,9 @@
 class Queue(
     base.StaffelnPersistentObject, base.StaffelnObject, base.StaffelnObjectDictCompat
 ):
-    VERSION = "1.0"
+    VERSION = "1.1"
+    # Version 1.0: Initial version
+    # Version 1.1: Add 'incremental' and 'reason' field
 
     dbapi = db_api.get_instance()
 
diff --git a/staffeln/objects/volume.py b/staffeln/objects/volume.py
index f365c0d..eded18e 100644
--- a/staffeln/objects/volume.py
+++ b/staffeln/objects/volume.py
@@ -8,7 +8,9 @@
 class Volume(
     base.StaffelnPersistentObject, base.StaffelnObject, base.StaffelnObjectDictCompat
 ):
-    VERSION = "1.0"
+    VERSION = "1.1"
+    # Version 1.0: Initial version
+    # Version 1.1: Add 'incremental' and 'created_at' field
 
     dbapi = db_api.get_instance()