diff --git a/code/modules/unit_tests/merge_type.dm b/code/modules/unit_tests/merge_type.dm
index 4a750cd130..373ffa2b66 100644
--- a/code/modules/unit_tests/merge_type.dm
+++ b/code/modules/unit_tests/merge_type.dm
@@ -9,7 +9,7 @@
 
 	var/list/paths = subtypesof(/obj/item/stack) - blacklist
 
-	for(var/stackpath in paths)
+	for(var/obj/item/stack/stackpath as anything in paths)
 		if(initial(stackpath.is_cyborg))
 			continue
 		var/obj/item/stack/stack = new stackpath