diff --git a/lib/internal/test_runner/test.js b/lib/internal/test_runner/test.js
index 2203bbd3497659..97d53c097261d7 100644
--- a/lib/internal/test_runner/test.js
+++ b/lib/internal/test_runner/test.js
@@ -149,7 +149,7 @@ function stopTest(timeout, signal) {
 
     disposeFunction = () => {
       abortListener[SymbolDispose]();
-      timer[SymbolDispose]();
+      clearTimeout(timer);
     };
   }
 
diff --git a/test/fixtures/test-runner/mock-timers-with-timeout.js b/test/fixtures/test-runner/mock-timers-with-timeout.js
new file mode 100644
index 00000000000000..4eb94ec5d6d8e9
--- /dev/null
+++ b/test/fixtures/test-runner/mock-timers-with-timeout.js
@@ -0,0 +1,43 @@
+'use strict';
+
+// Simulate @sinonjs/fake-timers: patch the timers module BEFORE
+// the test runner is loaded, so the test runner captures the patched
+// versions at import time.
+const nodeTimers = require('node:timers');
+const originalSetTimeout = nodeTimers.setTimeout;
+const originalClearTimeout = nodeTimers.clearTimeout;
+
+const fakeTimers = new Map();
+let nextId = 1;
+
+nodeTimers.setTimeout = (fn, delay, ...args) => {
+  const id = nextId++;
+  const timer = originalSetTimeout(fn, delay, ...args);
+  fakeTimers.set(id, timer);
+  // Sinon fake timers return an object with unref/ref but without
+  // Symbol.dispose, which would cause the test runner to throw.
+  return { id, unref() {}, ref() {} };
+};
+
+nodeTimers.clearTimeout = (id) => {
+  if (id != null && typeof id === 'object') id = id.id;
+  const timer = fakeTimers.get(id);
+  if (timer) {
+    originalClearTimeout(timer);
+    fakeTimers.delete(id);
+  }
+};
+
+// Now load the test runner - it will capture our patched setTimeout/clearTimeout
+const { test } = require('node:test');
+
+test('test with fake timers and timeout', { timeout: 10_000 }, () => {
+  // This test verifies that the test runner works when setTimeout returns
+  // an object without Symbol.dispose (like sinon fake timers).
+  // Previously, the test runner called timer[Symbol.dispose]() which would
+  // throw TypeError on objects returned by fake timer implementations.
+});
+
+// Restore
+nodeTimers.setTimeout = originalSetTimeout;
+nodeTimers.clearTimeout = originalClearTimeout;
diff --git a/test/parallel/test-runner-mock-timers-with-timeout.js b/test/parallel/test-runner-mock-timers-with-timeout.js
new file mode 100644
index 00000000000000..67f266851fe1ed
--- /dev/null
+++ b/test/parallel/test-runner-mock-timers-with-timeout.js
@@ -0,0 +1,14 @@
+'use strict';
+require('../common');
+const fixtures = require('../common/fixtures');
+const assert = require('node:assert');
+const { spawnSync } = require('node:child_process');
+const { test } = require('node:test');
+
+test('mock timers do not break test timeout cleanup', async () => {
+  const fixture = fixtures.path('test-runner', 'mock-timers-with-timeout.js');
+  const cp = spawnSync(process.execPath, ['--test', fixture], {
+    timeout: 30_000,
+  });
+  assert.strictEqual(cp.status, 0, `Test failed:\nstdout: ${cp.stdout}\nstderr: ${cp.stderr}`);
+});
diff --git a/tools/v8/fetch_deps.py b/tools/v8/fetch_deps.py
index 728e48eb14e899..055ffb50eafba5 100755
--- a/tools/v8/fetch_deps.py
+++ b/tools/v8/fetch_deps.py
@@ -24,6 +24,8 @@
     "deps_file"   : "DEPS",
     "managed"     : False,
     "custom_deps" : {
+      # Update depot_tools for compatibility with Python 3.12.
+      "v8/third_party/depot_tools"            : "https://chromium.googlesource.com/chromium/tools/depot_tools.git@284c5ccb591c3de4e9f71be4a4beb5d1916d5383",
       # These deps are already part of Node.js.
       "v8/base/trace_event/common"            : None,
       "v8/third_party/abseil-cpp"             : None,