diff --git a/lib/paymentPollingMain.ts b/lib/paymentPollingMain.ts
index fba69ce..73a90ba 100644
--- a/lib/paymentPollingMain.ts
+++ b/lib/paymentPollingMain.ts
@@ -57,7 +57,7 @@ export async function sendPrivateContentAfterPayment(
       const paymentHash = await resolvePaymentHashForPurchaseNote({
         articlePaymentHash: article.paymentHash,
         articleId,
-        zapReceiptId,
+        ...(zapReceiptId ? { zapReceiptId } : {}),
       })
       const category = normalizePurchaseNoteCategory(article.category)
 
@@ -83,9 +83,7 @@ export async function sendPrivateContentAfterPayment(
   return logPaymentResult(result, articleId, recipientPubkey, amount)
 }
 
-function normalizePurchaseNoteCategory(
-  category: 'author-presentation' | 'science-fiction' | 'scientific-research' | string
-): 'science-fiction' | 'scientific-research' | undefined {
+function normalizePurchaseNoteCategory(category: string | undefined): 'science-fiction' | 'scientific-research' | undefined {
   if (category === 'science-fiction' || category === 'scientific-research') {
     return category
   }