diff --git a/runtime/bin/file_system_watcher_macos.cc b/runtime/bin/file_system_watcher_macos.cc
index b73c0d13..88d6986 100644
--- a/runtime/bin/file_system_watcher_macos.cc
+++ b/runtime/bin/file_system_watcher_macos.cc
@@ -82,81 +82,36 @@
     void set_ref(FSEventStreamRef ref) { ref_ = ref; }
 
     void Start() {
-      // Schedule StartCallback to be executed in the RunLoop.
-      CFRunLoopTimerContext context;
-      memset(&context, 0, sizeof(context));
-      context.info = this;
-      CFRunLoopTimerRef timer =
-          CFRunLoopTimerCreate(NULL, 0, 0, 0, 0, Node::StartCallback, &context);
-      CFRunLoopAddTimer(watcher_->run_loop_, timer, kCFRunLoopCommonModes);
-      CFRelease(timer);
-      watcher_->monitor_.Enter();
-      while (!ready_) {
-        watcher_->monitor_.Wait(Monitor::kNoTimeout);
-      }
-      watcher_->monitor_.Exit();
-    }
-
-    static void StartCallback(CFRunLoopTimerRef timer, void* info) {
-      Node* node = reinterpret_cast<Node*>(info);
-      ASSERT(Thread::Compare(node->watcher_->threadId_,
-                             Thread::GetCurrentThreadId()));
       FSEventStreamContext context;
       memset(&context, 0, sizeof(context));
-      context.info = reinterpret_cast<void*>(node);
+      context.info = reinterpret_cast<void*>(this);
       CFArrayRef array = CFArrayCreate(
-          NULL, reinterpret_cast<const void**>(&node->path_ref_), 1, NULL);
+          NULL, reinterpret_cast<const void**>(&path_ref_), 1, NULL);
       FSEventStreamRef ref = FSEventStreamCreate(
           NULL, Callback, &context, array, kFSEventStreamEventIdSinceNow, 0.10,
           kFSEventStreamCreateFlagFileEvents);
       CFRelease(array);
 
-      node->set_ref(ref);
+      set_ref(ref);
+      ready_.store(true, std::memory_order_release);
 
-      FSEventStreamScheduleWithRunLoop(node->ref_, node->watcher_->run_loop_,
+      FSEventStreamScheduleWithRunLoop(ref_, watcher_->run_loop_,
                                        kCFRunLoopDefaultMode);
 
-      FSEventStreamStart(node->ref_);
-      FSEventStreamFlushSync(node->ref_);
-
-      node->watcher_->monitor_.Enter();
-      node->ready_ = true;
-      node->watcher_->monitor_.Notify();
-      node->watcher_->monitor_.Exit();
+      FSEventStreamStart(ref_);
+      FSEventStreamFlushSync(ref_);
     }
 
     void Stop() {
-      // Schedule StopCallback to be executed in the RunLoop.
       ASSERT(ready_);
-      CFRunLoopTimerContext context;
-      memset(&context, 0, sizeof(context));
-      context.info = this;
-      CFRunLoopTimerRef timer =
-          CFRunLoopTimerCreate(NULL, 0, 0, 0, 0, StopCallback, &context);
-      CFRunLoopAddTimer(watcher_->run_loop_, timer, kCFRunLoopCommonModes);
-      CFRelease(timer);
-      watcher_->monitor_.Enter();
-      while (ready_) {
-        watcher_->monitor_.Wait(Monitor::kNoTimeout);
-      }
-      watcher_->monitor_.Exit();
-    }
-
-    static void StopCallback(CFRunLoopTimerRef timer, void* info) {
-      Node* node = reinterpret_cast<Node*>(info);
-      ASSERT(Thread::Compare(node->watcher_->threadId_,
-                             Thread::GetCurrentThreadId()));
-      FSEventStreamStop(node->ref_);
-      FSEventStreamInvalidate(node->ref_);
-      FSEventStreamRelease(node->ref_);
-      node->watcher_->monitor_.Enter();
-      node->ready_ = false;
-      node->watcher_->monitor_.Notify();
-      node->watcher_->monitor_.Exit();
+      FSEventStreamStop(ref_);
+      FSEventStreamInvalidate(ref_);
+      FSEventStreamRelease(ref_);
+      ready_.store(false, std::memory_order_release);
     }
 
     FSEventsWatcher* watcher() const { return watcher_; }
-    bool ready() const { return ready_; }
+    bool ready() const { return ready_.load(std::memory_order_acquire); }
     intptr_t base_path_length() const { return base_path_length_; }
     int read_fd() const { return read_fd_; }
     int write_fd() const { return write_fd_; }
@@ -164,7 +119,7 @@
 
    private:
     FSEventsWatcher* watcher_;
-    bool ready_;
+    std::atomic<bool> ready_;
     intptr_t base_path_length_;
     CFStringRef path_ref_;
     int read_fd_;
@@ -266,8 +221,6 @@
     Node* node = reinterpret_cast<Node*>(client);
     ASSERT(Thread::Compare(node->watcher()->threadId_,
                            Thread::GetCurrentThreadId()));
-    // `ready` is set on same thread as this callback is invoked, so we don't
-    // need to lock here.
     if (!node->ready()) {
       return;
     }
diff --git a/tests/language/closure/tearoff_super_default_test.dart b/tests/language/closure/tearoff_super_default_test.dart
new file mode 100644
index 0000000..1e30932
--- /dev/null
+++ b/tests/language/closure/tearoff_super_default_test.dart
@@ -0,0 +1,85 @@
+// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:expect/expect.dart';
+
+class A1 {
+  final int _i1;
+  A1(this._i1);
+  toString() => 'A1($_i1)';
+
+  String foo(int i, [String s = 'A1.s']) => '$this.A1.foo($i, $s)';
+}
+
+class B1 extends A1 {
+  B1() : super(100);
+  toString() => 'B1($_i1)';
+
+  String foo(int i, [String s = 'B1.s']) => '$this.B1.foo($i, $s)';
+
+  String Function(int, [String]) getsuperfoo() => super.foo;
+  String callsuperfoo1(int i) => super.foo(i);
+  String callsuperfoo2(int i, String s) => super.foo(i, s);
+}
+
+class A2 {
+  final int _i2;
+  A2(this._i2);
+  toString() => 'A2($_i2)';
+
+  String foo(int i, [String s = 'A2.s']) => '$this.A2.foo($i, $s)';
+}
+
+class B2 extends A2 {
+  B2() : super(200);
+  toString() => 'B2($_i2)';
+
+  String foo(int i, [String s = 'B2.s']) => '$this.B2.foo($i, $s)';
+
+  String Function(int, [String]) getsuperfoo() => super.foo;
+  String callsuperfoo1(int i) => super.foo(i);
+  String callsuperfoo2(int i, String s) => super.foo(i, s);
+}
+
+void main() {
+  // The A1/B1 sequence and A2/B2 sequence do similar tests but in a different
+  // order. The super-getter is called first in ths A1/B1 sequence, but after
+  // the regular getters in the A2/B2 sequence.
+
+  // -------- A1/B1
+
+  final b1superfoo = B1().getsuperfoo();
+
+  Expect.equals('B1(100).A1.foo(50, A1.s)', b1superfoo(50));
+  Expect.equals('B1(100).A1.foo(51, xxxx)', b1superfoo(51, 'xxxx'));
+
+  final a1foo = A1(20).foo;
+  final b1foo = B1().foo;
+
+  Expect.equals('A1(20).A1.foo(52, A1.s)', a1foo(52));
+  Expect.equals('A1(20).A1.foo(53, xxxx)', a1foo(53, 'xxxx'));
+  Expect.equals('B1(100).B1.foo(54, B1.s)', b1foo(54));
+  Expect.equals('B1(100).B1.foo(55, xxxx)', b1foo(55, 'xxxx'));
+
+  Expect.equals('B1(100).A1.foo(56, A1.s)', B1().callsuperfoo1(56));
+  Expect.equals('B1(100).A1.foo(57, xxxx)', B1().callsuperfoo2(57, 'xxxx'));
+
+  // -------- A2/B2
+
+  final a2foo = A2(20).foo;
+  final b2foo = B2().foo;
+
+  Expect.equals('A2(20).A2.foo(60, A2.s)', a2foo(60));
+  Expect.equals('A2(20).A2.foo(61, xxxx)', a2foo(61, 'xxxx'));
+  Expect.equals('B2(200).B2.foo(62, B2.s)', b2foo(62));
+  Expect.equals('B2(200).B2.foo(63, xxxx)', b2foo(63, 'xxxx'));
+
+  Expect.equals('B2(200).A2.foo(64, A2.s)', B2().callsuperfoo1(64));
+  Expect.equals('B2(200).A2.foo(65, xxxx)', B2().callsuperfoo2(65, 'xxxx'));
+
+  final b2superfoo = B2().getsuperfoo();
+
+  Expect.equals('B2(200).A2.foo(66, A2.s)', b2superfoo(66));
+  Expect.equals('B2(200).A2.foo(67, xxxx)', b2superfoo(67, 'xxxx'));
+}
diff --git a/tools/VERSION b/tools/VERSION
index f039084..c387783 100644
--- a/tools/VERSION
+++ b/tools/VERSION
@@ -27,5 +27,5 @@
 MAJOR 2
 MINOR 14
 PATCH 0
-PRERELEASE 163
+PRERELEASE 164
 PRERELEASE_PATCH 0
\ No newline at end of file