diff --git a/public/main.js b/public/main.js
index e922c44e..c0ac9d11 100644
--- a/public/main.js
+++ b/public/main.js
@@ -187,7 +187,7 @@ const onZoom = debounce(function () {
 }, 50);
 const zoom = d3.zoom().scaleExtent([1, 20]).on("zoom", onZoom);
 
-let mapCoordinates = {}; // map coordinates on globe
+var mapCoordinates = {}; // map coordinates on globe
 let populationRate = +byId("populationRateInput").value;
 let distanceScale = +byId("distanceScaleInput").value;
 let urbanization = +byId("urbanizationInput").value;