diff --git a/init.lua b/init.lua
index 16aa90a..8269abb 100644
--- a/init.lua
+++ b/init.lua
@@ -10,7 +10,7 @@ local depmod = modutils.get_depend_checker(modname)
 
 local function filter(name, def)
 	-- disable carpets from loaded modules but not defined in dependency
-	if not depmod:check_depend(def.mod_origin) then
+	if not depmod:check_depend_by_itemname(name) then
 		return false
 	end
 
diff --git a/modutils.lua b/modutils.lua
index b7634c5..3f667dc 100644
--- a/modutils.lua
+++ b/modutils.lua
@@ -1,9 +1,39 @@
 local modutils = {}
 
-local function check_depend(this, modname)
+-- class methods
+function modutils.get_modname_by_itemname(itemname)
+	local def = minetest.registered_items[itemname]
+	if def then
+		return def.mod_origin
+	else --not loaded item
+		local delimpos = string.find(itemname, ":")
+		if delimpos then
+			return string.sub(itemname, 1,  delimpos - 1)
+		else
+			return nil
+		end
+	end
+
+end
+
+-- object methods
+local function check_depend(this, modname, deptype)
 	local depends = this.depends
 	if depends[modname] then
-		return true
+		if not deptype then  --"required" or "optional" only
+			return true
+		else
+			return (depends[modname] == deptype)
+		end
+	else
+		return false
+	end
+end
+
+local function check_depend_by_itemname(this, itemname, deptype)
+	local modname = modutils.get_modname_by_itemname(itemname)
+	if modname then
+		return this:check_depend(modname, deptype)
 	else
 		return false
 	end
@@ -14,7 +44,9 @@ function modutils.get_depend_checker(modname)
 	local this = { }
 	this.modname = modname
 	this.depends = {} -- depends.txt parsed
-	this.check_depend = check_depend -- method
+	this.check_depend = check_depend
+	this.check_depend_by_itemname = check_depend_by_itemname
+
 
 	-- get module path
 	local modpath = minetest.get_modpath(modname)
@@ -32,8 +64,10 @@ function modutils.get_depend_checker(modname)
 	for line in dependsfile:lines() do
 		if line:sub(-1) == "?" then
 			line = line:sub(1, -2)
+			this.depends[line] = "optional"
+		else
+			this.depends[line] = "required"
 		end
-		this.depends[line] = true
 	end
 
 	return this