diff --git a/frontend/index.js b/frontend/index.js
index 8fba713..9b14bc0 100644
--- a/frontend/index.js
+++ b/frontend/index.js
@@ -430,6 +430,8 @@ $('button').click(function () {
 function challengeEthereum(id, data) {
     console.log('Challenging task N ' + data + ' on Ethereum!');
     contractInstance.challenge.sendTransaction(data, function (err, txHash) {
-        $('#challenge-' + id).text('See tx on Etherscan!').attr("onclick", "window.open('https://rinkeby.etherscan.io/tx/" + txHash + "')");
+        if (!err) {
+            $('#challenge-' + id).text('See tx on Etherscan!').attr("onclick", "window.open('https://rinkeby.etherscan.io/tx/" + txHash + "')");
+        }
     });
 }