4 files changed, 56 insertions, 2 deletions
diff --git a/cli/tests/fix_worker_dispatchevent.ts b/cli/tests/fix_worker_dispatchevent.ts
new file mode 100644
index 000000000..1b73b52dc
--- /dev/null
+++ b/cli/tests/fix_worker_dispatchevent.ts
@@ -0,0 +1,43 @@
+const code = `
+addEventListener("message", () => {
+  postMessage("pong");
+});
+
+const context = new EventTarget();
+
+Object.defineProperty(globalThis, "dispatchEvent", {
+  value: context.dispatchEvent.bind(context),
+  writable: true,
+  enumerable: true,
+  configurable: true,
+});
+
+postMessage("start");
+`;
+
+const blob = new Blob([code], { type: "application/javascript" });
+
+const url = URL.createObjectURL(blob);
+
+const worker = new Worker(url, { type: "module" });
+
+let terminated = false;
+
+worker.addEventListener("message", (evt) => {
+  if (evt.data === "start") {
+    worker.postMessage("ping");
+  } else if (evt.data === "pong") {
+    worker.terminate();
+    terminated = true;
+    console.log("success");
+  } else {
+    throw new Error("unexpected message from worker");
+  }
+});
+
+setTimeout(() => {
+  if (!terminated) {
+    worker.terminate();
+    throw new Error("did not receive message from worker in time");
+  }
+}, 2000);
diff --git a/cli/tests/fix_worker_dispatchevent.ts.out b/cli/tests/fix_worker_dispatchevent.ts.out
new file mode 100644
index 000000000..2e9ba477f
--- /dev/null
+++ b/cli/tests/fix_worker_dispatchevent.ts.out
@@ -0,0 +1 @@
+success
diff --git a/cli/tests/integration_tests.rs b/cli/tests/integration_tests.rs
index bc67d5479..3d606b2a5 100644
--- a/cli/tests/integration_tests.rs
+++ b/cli/tests/integration_tests.rs
@@ -3972,6 +3972,11 @@ console.log("finish");
     output: "fix_tsc_file_exists.out",
   });
 
+  itest!(fix_worker_dispatchevent {
+    args: "run --quiet --reload fix_worker_dispatchevent.ts",
+    output: "fix_worker_dispatchevent.ts.out",
+  });
+
   itest!(es_private_fields {
     args: "run --quiet --reload es_private_fields.js",
     output: "es_private_fields.js.out",
diff --git a/runtime/js/99_main.js b/runtime/js/99_main.js
index f196f3008..aac6fc0ea 100644
--- a/runtime/js/99_main.js
+++ b/runtime/js/99_main.js
@@ -82,7 +82,12 @@ delete Object.prototype.__proto__;
   }
 
   let isClosing = false;
+  let globalDispatchEvent;
+
   async function pollForMessages() {
+    if (!globalDispatchEvent) {
+      globalDispatchEvent = globalThis.dispatchEvent.bind(globalThis);
+    }
     while (!isClosing) {
       const bufferMsg = await core.opAsync("op_worker_get_message");
       const data = core.deserialize(bufferMsg);
@@ -96,7 +101,7 @@ delete Object.prototype.__proto__;
         if (globalThis.onmessage) {
           await globalThis.onmessage(msgEvent);
         }
-        globalThis.dispatchEvent(msgEvent);
+        globalDispatchEvent(msgEvent);
       } catch (e) {
         let handled = false;
 
@@ -120,7 +125,7 @@ delete Object.prototype.__proto__;
           handled = ret === true;
         }
 
-        globalThis.dispatchEvent(errorEvent);
+        globalDispatchEvent(errorEvent);
         if (errorEvent.defaultPrevented) {
           handled = true;
         }