diff --git a/machines.lua b/machines.lua
index 495f2ea..120b7fe 100644
--- a/machines.lua
+++ b/machines.lua
@@ -896,7 +896,9 @@ definition.on_timer=function(pos,elapsed)
 	return shouldRerunTimer
 end
 if industrialtest.mclAvailable then
-	definition.groups.not_in_creative_inventory=1
+	definition.groups={
+		not_in_creative_inventory=1
+	}
 	definition._doc_items_create_entry=false
 end
 minetest.register_node("industrialtest:iron_furnace_active",definition)