diff --git a/denops/@denops-private/worker_test.ts b/denops/@denops-private/worker_test.ts
index 9fa0ed96..ae1fa870 100644
--- a/denops/@denops-private/worker_test.ts
+++ b/denops/@denops-private/worker_test.ts
@@ -49,10 +49,13 @@ function stubConsole() {
 
 function stubMessage() {
   const workerGlobal = globalThis as DedicatedWorkerGlobalScope;
+  // Use separate sandboxes so that stubs are restored before the defined
+  // properties are removed.
+  const defineSandbox = sinon.createSandbox();
   const sandbox = sinon.createSandbox();
-  sandbox.define(workerGlobal, "postMessage", () => {});
+  defineSandbox.define(workerGlobal, "postMessage", () => {});
   const postMessage = sandbox.stub(workerGlobal, "postMessage");
-  sandbox.define(workerGlobal, "onmessage", null);
+  defineSandbox.define(workerGlobal, "onmessage", null);
   const onmessage = sandbox.stub(workerGlobal, "onmessage");
   const fakeHostMessage = (data: unknown) => {
     workerGlobal.onmessage?.(new MessageEvent("message", { data }));
@@ -64,6 +67,7 @@ function stubMessage() {
     fakeHostMessage,
     [Symbol.dispose]() {
       sandbox.restore();
+      defineSandbox.restore();
     },
   };
 }
diff --git a/tests/denops/testutil/shared_server_test.ts b/tests/denops/testutil/shared_server_test.ts
index 1e3ac894..ddc8f1f1 100644
--- a/tests/denops/testutil/shared_server_test.ts
+++ b/tests/denops/testutil/shared_server_test.ts
@@ -107,13 +107,15 @@ Deno.test("useSharedServer()", async (t) => {
 
   await t.step("rejects if the server startup times out (flaky)", async () => {
     await retry(async () => {
-      await assertRejects(
+      // NOTE: The message of the timeout error differs between Deno versions,
+      // so check the error name instead.
+      const error = await assertRejects(
         async () => {
           await using _server = await useSharedServer({ timeout: 0 });
         },
-        Error,
-        "Signal timed out",
+        DOMException,
       );
+      assertEquals(error.name, "TimeoutError");
     });
   });
 });