diff --git a/sffcEncoder.js b/sffcEncoder.js
index 9ab8f3e..4e5e20d 100644
--- a/sffcEncoder.js
+++ b/sffcEncoder.js
@@ -64,7 +64,7 @@ var intToFloatArray = function (number, n) {
 }
 
 var padLeadingZeros = function (hex, byteSize) {
-  return (hex.length === byteSize * 2) ? hex : padLeadingZeros('0' + hex, byteSize)
+  return hex.padStart(byteSize * 2, '0')
 }
 
 module.exports = {