diff --git a/mods/ITEMS/mcl_potions/functions.lua b/mods/ITEMS/mcl_potions/functions.lua
index fc03b9012..429c177bb 100644
--- a/mods/ITEMS/mcl_potions/functions.lua
+++ b/mods/ITEMS/mcl_potions/functions.lua
@@ -1833,7 +1833,7 @@ end
 function mcl_potions.give_effect_by_level(name, object, level, duration, no_particles)
 	if level == 0 then return false end
 	if not registered_effects[name] then
-		minetest.log("warning", "[mcl_potions] Trying to give unknown effect "..name)
+		minetest.log("warning", "[mcl_potions] Trying to give unknown effect "..tostring(name))
 		return false
 	end
 	if not registered_effects[name].uses_factor then