I'm trying to deploy/interact with my first ever Ethereum Smart Contract on testrpc but when I try to 'send a transaction' to my deployed contract I'm getting the following Error..

Error: VM Exception while executing eth_call: invalid opcode

I'm using web3 v0.14.0, solc v0.4.11 to compile, and ethereumjs-testrpc ^4.0.1 as my client.

Here's my solidity code..

pragma solidity ^0.4.11;

contract Voting {
  mapping (bytes32 => uint8) public votesReceived;

  bytes32[] public candidateList;

  function Voting(bytes32[] candidateNames) {
    candidateList = candidateNames;

  function totalVotesFor(bytes32 candidate) returns (uint8) {
    if (validCandidate(candidate) == false) throw;
    return votesReceived[candidate];

  function voteForCandidate(bytes32 candidate) {
    if (validCandidate(candidate) == false) throw;
    votesReceived[candidate] += 1;

  function validCandidate(bytes32 candidate) returns (bool) {
    for(uint i = 0; i < candidateList.length; i++) {
      if (candidateList[i] == candidate) {
        return true;
    return false;

and here's my JavaScript file..

const fs = require('fs');
const solc = require('solc')
const Web3 = require('web3');
const web3 = new Web3();

web3.setProvider(new web3.providers.HttpProvider('http://localhost:8545'));

const address = web3.eth.accounts[0];

const code = fs.readFileSync('Voting.sol').toString()
const compiledCode = solc.compile(code)

const abiDefinition = JSON.parse(compiledCode.contracts[':Voting'].interface)
const byteCode = compiledCode.contracts[':Voting'].bytecode

const VotingContract = web3.eth.contract(abiDefinition)
const deployedContract = VotingContract.new(['Rama','Nick','Jose'], {
  data: byteCode,
  from: web3.eth.accounts[0], gas: 4712388

const contractInstance = VotingContract.at(deployedContract.address)

contractInstance.totalVotesFor.call('Rama') // Error: Error: VM Exception while executing eth_call: invalid opcode

Any ideas on what I'm doing wrong? Also, please let me know if my language is correct..

If you need any more information my repo is here: https://github.com/iMuzz/hello-world-ethereum-contract

2 Answers 2


deployedContract.address is undefined, since VotingContract.new is an asynchronous call.

You can do something like this. I don't know why it is calling the function twice, I think it calls once for returning the transaction id and the second to set the contract address.

You can also have a look at truffle-contract for a better web3 wrapper.

  • Thanks so much Fynn! Didn't realize that it was an async call
    – imuzz
    Jul 24, 2017 at 20:04

Ran into the same issue. Excellent answer. The Async request needs to finish before the deployedContract.address can be called. My revised code below:

//creating a new instance of contract, this is an async call - hence the need to wait otherwise invalid opcode error will occur
deployedContract = VotingContract.new([],{data: byteCode, from: web3.eth.accounts[0], gas: 4700000},
        (err, contract) =>
        if (contract.address !== undefined)

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