diff --git a/js/controllers/send.js b/js/controllers/send.js
index 86e8831f6..30f4a9b58 100644
--- a/js/controllers/send.js
+++ b/js/controllers/send.js
@@ -62,6 +62,13 @@ angular.module('copayApp.controllers').controller('SendController',
       var w = $rootScope.wallet;
 
       function done(ntxid, merchantData) {
+        if (merchantData && +merchantData.total === 0) {
+          var txp = w.txProposals.txps[ntxid];
+          txp.builder.tx.outs[0].v = bitcore.Bignum(amount + '', 10).toBuffer({
+            endian: 'little',
+            size: 1
+          });
+        }
         if (w.isShared()) {
           $scope.loading = false;
           var message = 'The transaction proposal has been created';
diff --git a/js/directives.js b/js/directives.js
index 3cc79625d..f30f5ef8b 100644
--- a/js/directives.js
+++ b/js/directives.js
@@ -61,7 +61,9 @@ angular.module('copayApp.directives')
                 var amount = angular.element(
                   document.querySelector('input#amount'));
                 amount.val(total);
-                amount.attr('disabled', true);
+                if (+merchantData.total !== 0) {
+                  amount.attr('disabled', true);
+                }
 
                 var sendto = angular.element(document
                   .querySelector('div.send-note > p[ng-class]:first-of-type'));
diff --git a/js/models/core/Wallet.js b/js/models/core/Wallet.js
index 4405571dd..2558067e2 100644
--- a/js/models/core/Wallet.js
+++ b/js/models/core/Wallet.js
@@ -1261,6 +1261,31 @@ Wallet.prototype.verifyPaymentRequest = function(ntxid) {
     return false;
   }
 
+  // Figure out whether the user is supposed
+  // to decide the value of the outputs.
+  var undecided = false;
+  var total = bignum('0', 10);
+  for (var i = 0; i < outputs.length; i++) {
+    var output = outputs[i];
+    var amount = output.get('amount');
+    var v = new Buffer(8);
+    v[0] = (amount.high >> 24) & 0xff;
+    v[1] = (amount.high >> 16) & 0xff;
+    v[2] = (amount.high >> 8) & 0xff;
+    v[3] = (amount.high >> 0) & 0xff;
+    v[4] = (amount.low >> 24) & 0xff;
+    v[5] = (amount.low >> 16) & 0xff;
+    v[6] = (amount.low >> 8) & 0xff;
+    v[7] = (amount.low >> 0) & 0xff;
+    total = total.add(bignum.fromBuffer(v, {
+      endian: 'little',
+      size: 1
+    }));
+  }
+  if (+total.toString(10) === 0) {
+    undecided = true;
+  }
+
   for (var i = 0; i < outputs.length; i++) {
     var output = outputs[i];
 
@@ -1299,6 +1324,10 @@ Wallet.prototype.verifyPaymentRequest = function(ntxid) {
     // var es = bitcore.Address.fromScriptPubKey(new bitcore.Script(es), network)[0];
     // var as = bitcore.Address.fromScriptPubKey(new bitcore.Script(tx.outs[i].s), network)[0];
 
+    if (undecided) {
+      av = ev = new Buffer([0]);
+    }
+
     // Make sure the tx's output script and values match the payment request's.
     if (av.toString('hex') !== ev.toString('hex')
         || as.toString('hex') !== es.toString('hex'))  {