diff -r 2a19d61f4ae4 -r 2187643b8e20 util/startup.lua
--- a/util/startup.lua	Mon Oct 05 21:45:02 2020 +0200
+++ b/util/startup.lua	Mon Oct 05 21:54:17 2020 +0200
@@ -260,7 +260,7 @@
 end
 
 function startup.setup_plugin_install_path()
-	local installer_plugin_path = config.get("*", "installer_plugin_path") or CFG_DATADIR.."/custom_plugins";
+	local installer_plugin_path = config.get("*", "installer_plugin_path") or (CFG_DATADIR or "data").."/custom_plugins";
 	local path_sep = package.config:sub(3,3);
 	-- TODO Figure out what this should be relative to, because CWD could be anywhere
 	installer_plugin_path = config.resolve_relative_path(require "lfs".currentdir(), installer_plugin_path);