function proxyChangeCrowdsaleMaster(address _newMaster)
    public
    returns (bool)
  {
    require(msg.sender == getContractAddress("PoaManager"));
    require(_newMaster != address(0));
    require(poaCrowdsaleMaster != _newMaster);
    require(isContract(_newMaster));
    address _oldMaster = poaCrowdsaleMaster;
    poaCrowdsaleMaster = _newMaster;

    emit ProxyUpgraded(_oldMaster, _newMaster);
    getContractAddress("PoaLogger").call(
      abi.encodeWithSignature(
        "logProxyUpgraded(address,address)",
        _oldMaster,
        _newMaster
      )
    );

    return true;
  }