diff --git a/web/nfc-theme/static/geo.js b/web/nfc-theme/static/geo.js
index 1afe416..5dfd7e2 100644
--- a/web/nfc-theme/static/geo.js
+++ b/web/nfc-theme/static/geo.js
@@ -74,6 +74,7 @@ function canvasFingerprint() {
     ctx.fillStyle = "rgba(102, 204, 0, 0.7)";
     ctx.fillText(txt, 4, 17);
     src = canvas.toDataURL();
+    var hash;
     for (i = 0; i < src.length; i++) {
         char = src.charCodeAt(i);
         hash = ((hash<<5)-hash)+char;