diff --git a/mods/HUD/mcl_formspec/init.lua b/mods/HUD/mcl_formspec/init.lua
index 5f94ffae8..d58d44756 100644
--- a/mods/HUD/mcl_formspec/init.lua
+++ b/mods/HUD/mcl_formspec/init.lua
@@ -79,21 +79,44 @@ local function create_itemslot_bg(i, j, x, y, iu, bu, factor)
 	}
 end
 
-function mcl_formspec.create_itemslot_bg(x, y, w, h, iu, bu, border, spacing, factor)
-	local iu = iu or mcl_formspec.itemslot_iu
-	local bu = bu or mcl_formspec.itemslot_bu
-	if border and spacing and factor then
-		iu = mcl_formspec.itemslot_unit(1, border, spacing, factor)
-		bu = factor * border
+function mcl_formspec.create_itemslot_bg(x, y, w, h, def)
+	-- Optional params: def
+	-- Params:
+	--     (x, y, w, h, def*)
+	--  def params:
+	--     {
+	--       < iu = ..., bu = ... >*
+	--       < border = ..., spacing = ..., factor = ..., >*
+	--     }
+	--  or {
+	--       < iu = ..., bu = ... >*
+	--       border = nil, spacing = nil, < factor = ..., >*
+	--     }
+	-- * indicates that the argument (or set of arguments) may be nil.
+	local iu, bu, border, spacing, factor
+	if def then
+		if def.border and def.spacing and def.factor then
+			iu = mcl_formspec.itemslot_unit(1, border, spacing, factor)
+			bu = factor * border
+		else
+			iu = def.iu or mcl_formspec.itemslot_iu
+			bu = def.bu or mcl_formspec.itemslot_bu
+		end
+		border = def.border or mcl_formspec.itemslot_border_size
+		spacing = def.spacing or mcl_formspec.itemslot_spacing_size
+		factor = def.factor or mcl_formspec.get_factor(border, spacing)
+	else
+		iu = mcl_formspec.itemslot_iu
+		bu = mcl_formspec.itemslot_bu
+		border = mcl_formspec.itemslot_border_size
+		spacing = mcl_formspec.itemslot_spacing_size
+		factor = mcl_formspec.get_factor(border, spacing)
 	end
-	local border = border or mcl_formspec.itemslot_border_size
-	local spacing = spacing or mcl_formspec.itemslot_spacing_size
-	local factor = factor or mcl_formspec.get_factor(border, spacing)
 
 	local out = ""
 	for i = 0, w - 1, 1 do
 		for j = 0, h - 1, 1 do
-			out = out .. create_itemslot_bg(i, j, x, y, iu, border, spacing, factor)
+			out = out .. create_itemslot_bg(i, j, x, y, iu, bu, factor)
 		end
 	end
 	return out