diff --git a/src/engine/gameManager/ForgeManager.java b/src/engine/gameManager/ForgeManager.java
index 5221498c..756cbbae 100644
--- a/src/engine/gameManager/ForgeManager.java
+++ b/src/engine/gameManager/ForgeManager.java
@@ -130,7 +130,7 @@ public enum ForgeManager implements Runnable {
             // Set total cost for this production run
 
             workOrder.production_cost_total.putAll(workOrder.production_cost);
-            workOrder.production_cost_total.forEach((key, value) -> workOrder.production_cost_total.compute(key, (k, v) -> v * workOrder.total_to_produce));
+            workOrder.production_cost_total.forEach((key, value) -> workOrder.production_cost_total.put(key, value * workOrder.total_to_produce));
 
             // Deduct gold cost from building