--- a/util/set.lua	Fri Feb 16 08:23:15 2018 +0100
+++ b/util/set.lua	Fri Feb 16 08:23:26 2018 +0100
@@ -12,7 +12,7 @@
 
 local _ENV = nil;
 
-local set_mt = {};
+local set_mt = { __name = "set" };
 function set_mt.__call(set, _, k)
 	return next(set._items, k);
 end