diff --git a/chapter11/src/main/java/org/eternity/billing/step05/BasicRatePolicy.java b/chapter11/src/main/java/org/eternity/billing/step05/BasicRatePolicy.java
index 8a29834..d867dbb 100644
--- a/chapter11/src/main/java/org/eternity/billing/step05/BasicRatePolicy.java
+++ b/chapter11/src/main/java/org/eternity/billing/step05/BasicRatePolicy.java
@@ -8,7 +8,7 @@ public Money calculateFee(Phone phone) {
         Money result = Money.ZERO;
 
         for(Call call : phone.getCalls()) {
-            result.plus(calculateCallFee(call));
+            result = result.plus(calculateCallFee(call));
         }
 
         return result;