diff --git a/xray.js b/xray.js
index 9529f78..fa283de 100644
--- a/xray.js
+++ b/xray.js
@@ -588,7 +588,7 @@ function updateOverlay(points, clicked) {
     overlayCtx.globalCompositeOperation = "source-over";
 
     if (!paintMode)
-        overlayCtx.clearRect(0, 0, w, h);
+        overlayCtx.clearRect(0, 0, w / window.devicePixelRatio, h / window.devicePixelRatio);
 
     if (!paintMode || clicked) {
         points.forEach(point => {