diff --git a/BTCPayServer/Payments/Lightning/LightningLikePaymentData.cs b/BTCPayServer/Payments/Lightning/LightningLikePaymentData.cs
index 1ee352414..403c0e9ae 100644
--- a/BTCPayServer/Payments/Lightning/LightningLikePaymentData.cs
+++ b/BTCPayServer/Payments/Lightning/LightningLikePaymentData.cs
@@ -66,7 +66,7 @@ namespace BTCPayServer.Payments.Lightning
 
         public string GetPaymentProof()
         {
-            return Preimage.ToString();
+            return Preimage?.ToString();
         }
     }
 }