diff --git a/js/models/core/Wallet.js b/js/models/core/Wallet.js
index ce3a64347..c3163aea7 100644
--- a/js/models/core/Wallet.js
+++ b/js/models/core/Wallet.js
@@ -108,8 +108,8 @@ inherits(Wallet, events.EventEmitter);
 Wallet.builderOpts = {
   lockTime: null,
   signhash: bitcore.Transaction.SIGNHASH_ALL,
-  fee: null,
-  feeSat: null,
+  fee: undefined,
+  feeSat: undefined,
 };
 
 /**