Before revision:  In this paper, we systematically identify a set of 20 Solidity code smells that could affect the deployment and transaction costs of a smart contract, i. e.,\textit{cost smells .
After revision:  In this paper, we (i) identify a set of 20 Solidity code smells that could affect the deployment and transaction costs of a smart contract, i. e.,\textit{cost smells .