diff --git a/lib/wallet.js b/lib/wallet.js
index 580c3173e..131fd80ca 100644
--- a/lib/wallet.js
+++ b/lib/wallet.js
@@ -236,12 +236,14 @@ var zero = new utils.BN(0);
 var negative1 = new utils.BN(-1);
 var tenPower18 = new utils.BN('1000000000000000000');
 utils.defineProperty(Wallet, 'formatEther', function(wei, options) {
+
     if (typeof(wei) === 'number') {
         // @TODO: Warn if truncation will occur?
         wei = new utils.BN(wei);
     } else if (utils.isHexString(wei)) {
-        wei = new utils.BN(wei.substring(2));
+        wei = new utils.BN(wei.substring(2), 16);
     }
+
     if (!options) { options = {}; }
 
     if (!(wei instanceof utils.BN)) { throw new Error('invalid wei'); }