diff --git a/demo/benchmark.html b/demo/benchmark.html
index d0e5746..6a6602d 100644
--- a/demo/benchmark.html
+++ b/demo/benchmark.html
@@ -9,6 +9,10 @@
     .tip {
       font-style: italic;
     }
+
+    #status {
+      color: red;
+    }
   </style>
 </head>
 
diff --git a/demo/benchmark.ts b/demo/benchmark.ts
index 1754510..2859e8a 100644
--- a/demo/benchmark.ts
+++ b/demo/benchmark.ts
@@ -101,4 +101,13 @@ function updateCost(id: string) {
   getElById(id).textContent = `${~~(performance.now() - startTime)}ms`;
 }
 
+// clear
+await file(fileName).remove();
+tx = db.transaction('data', 'readwrite');
+store = tx.objectStore('data');
+for (const k of idbKeys) {
+  await store.delete(k);
+}
+await tx.done;
+
 export default {};