diff --git a/js/main-window.js b/js/main-window.js
index 277c854f..ba630452 100644
--- a/js/main-window.js
+++ b/js/main-window.js
@@ -256,7 +256,7 @@ MainWindow = {
         ];
 
         // For each digit/node
-        for(i = 0; i < 4; i++) {
+        for(var i = 0; i < 4; i++) {
             var digit = digits[i];
             var digitNode = digitNodes[i];
             var shadeNode = shadeDigitNodes[i];
diff --git a/js/visualizer.js b/js/visualizer.js
index 1049a8af..4b32f2e0 100644
--- a/js/visualizer.js
+++ b/js/visualizer.js
@@ -55,7 +55,7 @@ Visualizer = {
     preRenderBar: function() {
         this.barCanvasCtx.fillStyle = this.colors[23];
         this.barCanvasCtx.fillRect(0,0,6,2);
-        for(i = 0; i <= 15; i++) {
+        for(var i = 0; i <= 15; i++) {
             var colorNumber = 17 - i;
             this.barCanvasCtx.fillStyle = this.colors[colorNumber];
             var y = 32 - (i*2);