diff --git a/lib/ssh.js b/lib/ssh.js
index 6480203a8..26d35f072 100644
--- a/lib/ssh.js
+++ b/lib/ssh.js
@@ -202,7 +202,7 @@ ssh.getPublicKeyFingerprint = function(key, options) {
 function _addBigIntegerToBuffer(buffer, val) {
   var hexVal = val.toString(16);
   // ensure 2s complement +ve
-  if(hexVal[0] >= '8') {
+  if(hexVal[0] >= '8' && (hexVal.length % 2 === 0)) {
     hexVal = '00' + hexVal;
   }
   var bytes = forge.util.hexToBytes(hexVal);