diff --git a/lib/string_decoder.js b/lib/string_decoder.js
index ffb04ffff56b84..a0bfd535ad8895 100644
--- a/lib/string_decoder.js
+++ b/lib/string_decoder.js
@@ -69,6 +69,7 @@ StringDecoder.prototype.write = function(buffer) {
   var charReceived = this.charReceived;
   var surrogateSize = this.surrogateSize;
   var encoding = this.encoding;
+  var charCode;
   // if our last write ended with an incomplete multibyte character
   while (charLength) {
     // determine how many remaining bytes this buffer has to offer for this char
@@ -96,7 +97,7 @@ StringDecoder.prototype.write = function(buffer) {
     charStr = charBuffer.toString(encoding, 0, charLength);
 
     // CESU-8: lead surrogate (D800-DBFF) is also the incomplete character
-    const charCode = charStr.charCodeAt(charStr.length - 1);
+    charCode = charStr.charCodeAt(charStr.length - 1);
     if (charCode >= 0xD800 && charCode <= 0xDBFF) {
       charLength += surrogateSize;
       charStr = '';
@@ -129,7 +130,7 @@ StringDecoder.prototype.write = function(buffer) {
   charStr += buffer.toString(encoding, 0, end);
 
   end = charStr.length - 1;
-  const charCode = charStr.charCodeAt(end);
+  charCode = charStr.charCodeAt(end);
   // CESU-8: lead surrogate (D800-DBFF) is also the incomplete character
   if (charCode >= 0xD800 && charCode <= 0xDBFF) {
     charLength += surrogateSize;