diff --git a/feeCalculator/src/main/java/org/example/FeeCalculator.java b/feeCalculator/src/main/java/org/example/FeeCalculator.java
index f7ecd2c..5edff4e 100644
--- a/feeCalculator/src/main/java/org/example/FeeCalculator.java
+++ b/feeCalculator/src/main/java/org/example/FeeCalculator.java
@@ -3,6 +3,10 @@ package org.example;
 public class FeeCalculator {
 
     public static double calculateFee(Visitor visitor, TicketType ticketType) {
+        if (TicketType.HALF_DAY != ticketType && TicketType.FULL_DAY != ticketType) {
+            throw new IllegalArgumentException("Invalid ticket type");
+        }
+        
         double fee = visitor.calculateFee(ticketType);
         return fee;
     }