diff --git a/static/js/tts-preview.js b/static/js/tts-preview.js
index 3ba9d32..6ac2d13 100644
--- a/static/js/tts-preview.js
+++ b/static/js/tts-preview.js
@@ -709,6 +709,8 @@ function perfHistoryAvatarHtml(entry) {
 }
 
 
+const PERF_HISTORY_TEXT_KEYS = ['backend', 'language', 'gender', 'voice', 'device'];
+
 function perfHistorySortValue(entry, key) {
   switch (key) {
     case 'backend': return String(entry.backend || '').toLowerCase();
@@ -716,21 +718,22 @@ function perfHistorySortValue(entry, key) {
     case 'gender': return String(perfHistoryGenderLabel(perfHistoryVoiceMeta(entry).gender) || '').toLowerCase();
     case 'voice': return String(entry.voice || '').toLowerCase();
     case 'device': return String(perfHistoryDeviceLabel(entry) || '').toLowerCase();
-    case 'avgLatencyMs': return Number(entry.avgLatencyMs);
-    case 'minLatencyMs': return Number(entry.minLatencyMs);
-    case 'avgRtf': return Number(entry.avgRtf);
-    case 'ts':
-    default: return Number(entry.ts);
+    default: return '';
   }
 }
 
+function perfHistoryNumericValue(entry, key) {
+  return Number(['avgLatencyMs', 'minLatencyMs', 'avgRtf'].includes(key) ? entry[key] : entry.ts);
+}
+
 function perfHistoryCompare(a, b) {
-  const av = perfHistorySortValue(a, PERF_HISTORY_SORT.key);
-  const bv = perfHistorySortValue(b, PERF_HISTORY_SORT.key);
+  const key = PERF_HISTORY_SORT.key;
   let result = 0;
-  if (typeof av === 'string' || typeof bv === 'string') {
-    result = String(av).localeCompare(String(bv), undefined, { numeric: true, sensitivity: 'base' });
+  if (PERF_HISTORY_TEXT_KEYS.includes(key)) {
+    result = perfHistorySortValue(a, key).localeCompare(perfHistorySortValue(b, key), undefined, { numeric: true, sensitivity: 'base' });
   } else {
+    const av = perfHistoryNumericValue(a, key);
+    const bv = perfHistoryNumericValue(b, key);
     const an = Number.isFinite(av) ? av : -Infinity;
     const bn = Number.isFinite(bv) ? bv : -Infinity;
     result = an === bn ? 0 : an - bn;