diff --git a/lib/helper.js b/lib/helper.js
index db58e3f..a9c6e52 100644
--- a/lib/helper.js
+++ b/lib/helper.js
@@ -138,7 +138,8 @@ var decryptAudioData = function(data, audioAesKey, audioAesIv, headerSize) {
   var remainder = (data.length - 12) % 16;
   var endOfEncodedData = data.length - remainder;
 
-  var decipher = crypto.createDecipheriv('aes-128-cbc', audioAesKey, audioAesIv);
+  var audioAesKeyBuffer = new Buffer(audioAesKey, 'binary');
+  var decipher = crypto.createDecipheriv('aes-128-cbc', audioAesKeyBuffer, audioAesIv);
   decipher.setAutoPadding(false);
 
   for (var i = headerSize, l = endOfEncodedData - 16; i <= l; i += 16) {