diff --git a/README.md b/README.md
index e59e834..12c0d13 100644
--- a/README.md
+++ b/README.md
@@ -51,4 +51,6 @@ The `i3`  inventory is 9 slots wide by default, such as Minecraft.
 
 Report bugs on the [**Bug Tracker**](https://github.com/minetest-mods/i3/issues).
 
+**Video review on YouTube:** https://www.youtube.com/watch?v=Xd14BCdEZ3o
+
 ![Preview](https://user-images.githubusercontent.com/7883281/142780121-564c1969-b95b-4cc9-99df-9f2362c67e07.png)
diff --git a/src/bags.lua b/src/bags.lua
index 0c7fe85..b654278 100644
--- a/src/bags.lua
+++ b/src/bags.lua
@@ -101,6 +101,18 @@ local function init_bags(player)
 		on_move = save_content,
 		on_put = save_content,
 		on_take = save_content,
+
+		allow_put = function(_, _, _, stack)
+			local meta = stack:get_meta()
+			local content = dslz(meta:get_string"content")
+
+			if content then
+				msg(name, "You cannot put a bag in another bag")
+				return 0, play_sound(name, "i3_cannot", 0.8)
+			end
+
+			return stack:get_count()
+		end,
 	}, name)
 
 	bag_content:set_size("main", 4*4)