diff --git a/app/static/index.html b/app/static/index.html
index 66b86fa..c75c326 100644
--- a/app/static/index.html
+++ b/app/static/index.html
@@ -311,7 +311,8 @@ function uptimeCell(pct, history) {
   const segs = hist.map((h, i) => {
     const ok = typeof h === 'boolean' ? h : h && h.ok;
     const data = typeof h === 'boolean' ? { ok } : h;
-    return `<span class="uptime-seg ${ok ? 'ok' : 'fail'}" data-seg='${JSON.stringify(data).replace(/'/g, "&#39;")}'></span>`;
+    const jsonStr = JSON.stringify(data).replace(/"/g, '&quot;').replace(/'/g, '&#39;');
+    return `<span class="uptime-seg ${ok ? 'ok' : 'fail'}" data-seg='${jsonStr}'></span>`;
   }).join('');
 
   const label = pct === null || pct === undefined ? '—' : `${pct}%`;