diff --git a/js/id/renderer/background.js b/js/id/renderer/background.js
index 752853e6b..54e3835ee 100644
--- a/js/id/renderer/background.js
+++ b/js/id/renderer/background.js
@@ -3,7 +3,7 @@ iD.Background = function() {
     var deviceRatio = (window.devicePixelRatio &&
         window.devicePixelRatio === 2) ? 0.5 : 1;
         // tileSize = (deviceRatio === 0.5) ? [128,128] : [256,256];
-    tileSize = [256, 256];
+    var tileSize = [256, 256];
 
     var tile = d3.geo.tile(),
         projection,