diff --git a/lib/circular_buffer.js b/lib/circular_buffer.js
index 1830ef3..049f599 100644
--- a/lib/circular_buffer.js
+++ b/lib/circular_buffer.js
@@ -1,4 +1,4 @@
-var CircularBuffer = module.exports = function(size) {
+let CircularBuffer = module.exports = function(size) {
   this.pos = 0;
   this._buf = [];
   this.size = size;