diff --git a/lib/model/txproposal.js b/lib/model/txproposal.js
index ee6896a..37b5e62 100644
--- a/lib/model/txproposal.js
+++ b/lib/model/txproposal.js
@@ -171,7 +171,7 @@ TxProposal.prototype._buildTx = function() {
     t.to(self.toAddress, self.amount);
   } else if (self.outputs) {
     _.each(self.outputs, function(o) {
-      $.checkState(!o.script != !o.toAddress, 'Output should have either toAddress or script specified');
+      $.checkState(o.script || o.toAddress, 'Output should have either toAddress or script specified');
       if (o.script) {
         t.addOutput(new Bitcore.Transaction.Output({
           script: o.script,