diff --git a/index.js b/index.js
index 991986f..08d7016 100644
--- a/index.js
+++ b/index.js
@@ -28,6 +28,10 @@ self.wasmhttp = {
     try {
       if (!wasm) throw TypeError('options.wasm must be defined')
 
+      addEventListener('activate', event => {
+        event.waitUntil(clients.claim())
+      })
+
       const handlerId = `${nextHandlerId++}`
       const handler = new Promise(resolve => handlerResolvers[handlerId] = resolve)