diff --git a/lib/model/txproposal.js b/lib/model/txproposal.js
index 7abea35..a05db2c 100644
--- a/lib/model/txproposal.js
+++ b/lib/model/txproposal.js
@@ -162,7 +162,7 @@ TxProposal.prototype._buildTx = function() {
   t.fee(self.fee);
 
   var totalInputs = _.sum(self.inputs, 'satoshis');
-  var totalOutputs = _.sum(self.outputs, 'satoshis');
+  var totalOutputs = _.sum(self.outputs, 'amount');
 
   if (totalInputs - totalOutputs - self.fee > 0 && self.changeAddress) {
     t.change(self.changeAddress.address);
@@ -182,9 +182,10 @@ TxProposal.prototype._buildTx = function() {
   }
 
   // Validate actual inputs vs outputs independently of Bitcore
-  var totalInputs = _.sum(t.inputs, 'satoshis');
+  var totalInputs = _.sum(t.inputs, 'output.satoshis');
   var totalOutputs = _.sum(t.outputs, 'satoshis');
 
+  $.checkState(totalInputs > 0 && totalOutputs > 0 && totalInputs >= totalOutputs);
   $.checkState(totalInputs - totalOutputs <= Defaults.MAX_TX_FEE);
 
   return t;