diff --git a/src/config.js b/src/config.js
index a4c65785..e69d25db 100644
--- a/src/config.js
+++ b/src/config.js
@@ -1,6 +1,6 @@
 
 // Heatmap Config stores default values and will be merged with instance config
-var HeatmapConfig = {
+let HeatmapConfig = {
   defaultRadius: 40,
   defaultRenderer: 'canvas2d',
   defaultGradient: { 0.25: "rgb(0,0,255)", 0.55: "rgb(0,255,0)", 0.85: "yellow", 1.0: "rgb(255,0,0)"},
@@ -11,4 +11,4 @@ var HeatmapConfig = {
   defaultYField: 'y',
   defaultValueField: 'value', 
   plugins: {}
-};
\ No newline at end of file
+};