diff --git a/lib/cmds/blockchain/blockchain.js b/lib/cmds/blockchain/blockchain.js
index 56b43b5ad..5598e91d3 100644
--- a/lib/cmds/blockchain/blockchain.js
+++ b/lib/cmds/blockchain/blockchain.js
@@ -125,6 +125,7 @@ Blockchain.prototype.initChainAndGetAddress = function() {
 };
 
 var BlockchainClient = function(blockchainConfig, client, env, isDev) {
+  // TODO add other clients at some point
   if (client === 'geth') {
     return new Blockchain({blockchainConfig, client: GethCommands, env, isDev});
   } else {
diff --git a/lib/contracts/accountParser.js b/lib/contracts/accountParser.js
index f2f56f8de..e2460bd6c 100644
--- a/lib/contracts/accountParser.js
+++ b/lib/contracts/accountParser.js
@@ -29,15 +29,23 @@ class AccountParser {
       if (!accountConfig.privateKey.startsWith('0x')) {
         accountConfig.privateKey = '0x' + accountConfig.privateKey;
       }
+      if (!web3.utils.isHexStrict(accountConfig.privateKey)) {
+        logger.warn(`Private key ending with ${accountConfig.privateKey.substr(accountConfig.privateKey.length - 5)} is not a HEX string`);
+        return null;
+      }
       return web3.eth.accounts.privateKeyToAccount(accountConfig.privateKey);
     }
     if (accountConfig.privateKeyFile) {
       let fileContent = fs.readFileSync(fs.dappPath(accountConfig.privateKeyFile)).toString();
       fileContent = fileContent.trim().split(/[,;]/);
-      return fileContent.map(key => {
+      return fileContent.map((key, index) => {
         if (!key.startsWith('0x')) {
           key = '0x' + key;
         }
+        if (!web3.utils.isHexStrict(key)) {
+          logger.warn(`Private key is not a HEX string in file ${accountConfig.privateKeyFile} at index ${index}`);
+          return null;
+        }
         return web3.eth.accounts.privateKeyToAccount(key);
       });
     }