diff --git a/plugins/portname/init.lua b/plugins/portname/init.lua
index 538c3c6475d..78e8da626b0 100644
--- a/plugins/portname/init.lua
+++ b/plugins/portname/init.lua
@@ -28,7 +28,7 @@ local portname = exports
 
 function portname.startplugin()
 	local json = require("json")
-	local ctrlrpath = lfs.subst_env(manager:options().entries.ctrlrpath:value():match("([^;]+)"))
+	local ctrlrpath = emu.subst_env(manager:options().entries.ctrlrpath:value():match("([^;]+)"))
 	local function get_filename(nosoft)
 		local filename
 		if emu.softname() ~= "" and not nosoft then