diff --git a/tosspay-mock/src/main/kotlin/com/sangdol/tosspaymock/web/dto/TosspayRequest.kt b/tosspay-mock/src/main/kotlin/com/sangdol/tosspaymock/web/dto/TosspayRequest.kt
index 984795d4..e38cf0eb 100644
--- a/tosspay-mock/src/main/kotlin/com/sangdol/tosspaymock/web/dto/TosspayRequest.kt
+++ b/tosspay-mock/src/main/kotlin/com/sangdol/tosspaymock/web/dto/TosspayRequest.kt
@@ -10,6 +10,6 @@ data class PaymentConfirmRequest(
 )
 
 data class PaymentCancelRequest(
-    val cancelAmount: Int?,
+    val cancelAmount: Int? = null,
     val cancelReason: String
 )