diff --git a/code/game/objects/items/stacks/stack.dm b/code/game/objects/items/stacks/stack.dm
index 285647aaec7..f29f8fdeb67 100644
--- a/code/game/objects/items/stacks/stack.dm
+++ b/code/game/objects/items/stacks/stack.dm
@@ -315,6 +315,8 @@
 	amount -= used
 	if(check)
 		zero_amount()
+	for(var/i in custom_materials)
+		custom_materials[i] = amount * mats_per_stack
 	update_icon()
 	update_weight()
 	return TRUE
@@ -413,6 +415,8 @@
 	if(!use(amount, TRUE, FALSE))
 		return FALSE
 	var/obj/item/stack/F = new type(user? user : drop_location(), amount, FALSE)
+	for(var/i in F.custom_materials)
+		custom_materials[i] -= F.custom_materials[i]
 	. = F
 	F.copy_evidences(src)
 	if(user)