diff --git a/lib/bip70/payment.js b/lib/bip70/payment.js
index cdb8da07..bc34b141 100644
--- a/lib/bip70/payment.js
+++ b/lib/bip70/payment.js
@@ -104,7 +104,7 @@ Payment.prototype.toRaw = function toRaw(writer) {
 
   for (i = 0; i < this.transactions.length; i++) {
     tx = this.transactions[i];
-    this.writeFieldBytes(2, tx.toRaw());
+    bw.writeFieldBytes(2, tx.toRaw());
   }
 
   for (i = 0; i < this.refundTo.length; i++) {