diff --git a/js/models/core/Wallet.js b/js/models/core/Wallet.js
index 4f16be2fd..5bccd710c 100644
--- a/js/models/core/Wallet.js
+++ b/js/models/core/Wallet.js
@@ -881,8 +881,8 @@ Wallet.prototype.receivePaymentRequest = function(options, pr, cb) {
       },
       signature: sig,
       ca: ca,
-      total: bignum('0')
-    }
+    },
+    total: bignum('0').toString(10)
   };
 
   return this.getUnspent(function(err, unspent) {
@@ -1050,6 +1050,10 @@ Wallet.prototype.createPaymentTxSync = function(options, merchantData, unspent)
     var signed = b.sign(keys);
   }
 
+  if (typeof merchantData.total === 'string') {
+    merchantData.total = bignum(merchantData.total, 10);
+  }
+
   merchantData.pr.pd.outputs.forEach(function(output, i) {
     var amount = output.get
       ? output.get('amount')