--- a/plugins/mod_groups.lua	Thu Feb 04 10:05:35 2016 +0100
+++ b/plugins/mod_groups.lua	Thu Feb 04 10:06:09 2016 +0100
@@ -82,7 +82,7 @@
 end
 
 function module.load()
-	groups_file = module:get_option_string("groups_file");
+	groups_file = module:get_option_path("groups_file", nil, "config");
 	if not groups_file then return; end
 
 	module:hook("roster-load", inject_roster_contacts);