diff --git a/appstore/model.go b/appstore/model.go
index f8b7ffe..f9c7e8c 100644
--- a/appstore/model.go
+++ b/appstore/model.go
@@ -105,7 +105,7 @@ type (
 		Quantity                    string        `json:"quantity"`
 		ProductID                   string        `json:"product_id"`
 		TransactionID               string        `json:"transaction_id"`
-		OriginalTransactionID       NumericString `json:"original_transaction_id"`
+		OriginalTransactionID       NumericString `json:"original_transaction_id,omitempty"`
 		WebOrderLineItemID          string        `json:"web_order_line_item_id,omitempty"`
 		PromotionalOfferID          string        `json:"promotional_offer_id"`
 		SubscriptionGroupIdentifier string        `json:"subscription_group_identifier"`
@@ -211,7 +211,7 @@ type (
 		ItemID               string `json:"item_id"`
 		ProductID            string `json:"product_id"`
 		PurchaseDate
-		OriginalTransactionID NumericString `json:"original_transaction_id"`
+		OriginalTransactionID NumericString `json:"original_transaction_id,omitempty"`
 		OriginalPurchaseDate
 		Quantity                  string        `json:"quantity"`
 		TransactionID             string        `json:"transaction_id"`
diff --git a/appstore/notification.go b/appstore/notification.go
index 086c236..70b4a22 100644
--- a/appstore/notification.go
+++ b/appstore/notification.go
@@ -66,7 +66,7 @@ type NotificationReceipt struct {
 	BID                       string        `json:"bid"`
 	BVRS                      string        `json:"bvrs"`
 	TransactionID             string        `json:"transaction_id"`
-	OriginalTransactionID     NumericString `json:"original_transaction_id"`
+	OriginalTransactionID     NumericString `json:"original_transaction_id,omitempty"`
 	IsTrialPeriod             string        `json:"is_trial_period"`
 	IsInIntroOfferPeriod      string        `json:"is_in_intro_offer_period"`
 
@@ -94,7 +94,7 @@ type SubscriptionNotification struct {
 
 	// Not show in raw notify body
 	Password              string        `json:"password"`
-	OriginalTransactionID NumericString `json:"original_transaction_id"`
+	OriginalTransactionID NumericString `json:"original_transaction_id,omitempty"`
 	AutoRenewAdamID       string        `json:"auto_renew_adam_id"`
 
 	// The primary key for identifying a subscription purchase.