diff --git a/app/Ninja/Repositories/InvoiceRepository.php b/app/Ninja/Repositories/InvoiceRepository.php
index c70ea5dc2b63..e584ff238cdd 100644
--- a/app/Ninja/Repositories/InvoiceRepository.php
+++ b/app/Ninja/Repositories/InvoiceRepository.php
@@ -336,7 +336,7 @@ class InvoiceRepository extends BaseRepository
             $account->save();
         }
 
-        if (isset($data['invoice_number']) && !$invoice->is_recurring) {
+        if (!empty($data['invoice_number']) && !$invoice->is_recurring) {
             $invoice->invoice_number = trim($data['invoice_number']);
         }