diff --git a/API.md b/API.md
index 68218a5..a3fc9bd 100644
--- a/API.md
+++ b/API.md
@@ -308,10 +308,10 @@ Returns a table of recipes and usages of `item`.
 If set, the mod will export all the cached recipes and usages in a JSON format
 to the given URL (HTTP support is required¹).
 
-#### `groups = {bag = <1-3>}`
+#### `groups = {bag = <1-4>}`
 
 The `bag` group in the item definition allows to extend the player inventory size
-given a number between 1 and 3.
+given a number between 1 and 4.
 
 ---
 
diff --git a/init.lua b/init.lua
index a2a4a1c..5176231 100644
--- a/init.lua
+++ b/init.lua
@@ -19,6 +19,7 @@ i3 = {
 		4*9 + 3,
 		4*9 + 6,
 		4*9 + 9,
+		4*9 + 25,
 	},
 
 	SUBCAT = {
diff --git a/src/bags.lua b/src/bags.lua
index 126b2e2..375b490 100644
--- a/src/bags.lua
+++ b/src/bags.lua
@@ -17,7 +17,6 @@ local function init_backpack(player)
 			end
 
 			msg(name, S"This is not a backpack")
-
 			return 0
 		end,
 
diff --git a/src/gui.lua b/src/gui.lua
index 08b02bd..6cbe085 100644
--- a/src/gui.lua
+++ b/src/gui.lua
@@ -139,13 +139,8 @@ local function get_inv_slots(data, fs)
 	   fmt("list[current_player;main;%f,%f;%u,1;]", inv_x, inv_y, i3.HOTBAR_LEN))
 
 	if bag then
-		if bag == 1 then
-			width, size = 10, 0.892
-		elseif bag == 2 then
-			width, size = 11, 0.8
-		elseif bag == 3 then
-			width, size = 12, 0.726
-		end
+		local params = {{10, 0.892}, {11, 0.8}, {12, 0.726}, {13, 0.663}}
+		width, size = unpack(params[bag])
 	end
 
 	fs(fmt("style_type[list;size=%f;spacing=%f]", size, spacing),