diff --git a/storage/itemgroup.lua b/storage/itemgroup.lua
index 75b0152..bf23726 100644
--- a/storage/itemgroup.lua
+++ b/storage/itemgroup.lua
@@ -1,6 +1,6 @@
 local Sentinel = require("storage.sentinel")
 
-local ItemGroup = Sentinel.tag({}, Sentinel.ITEMGROUP)
+local ItemGroup = Sentinel:tag({}, Sentinel.ITEMGROUP)
 ItemGroup.__index = ItemGroup
 
 --- Create a group of managed itemstacks