diff --git a/internal/test/fake_clock.cc b/internal/test/fake_clock.cc
index 57c6b29d..3f464ea6 100644
--- a/internal/test/fake_clock.cc
+++ b/internal/test/fake_clock.cc
@@ -21,6 +21,11 @@
 
 namespace nearby {
 
+FakeClock::~FakeClock() {
+  absl::MutexLock lock(&mutex_);
+  observers_.clear();
+}
+
 absl::Time FakeClock::Now() const {
   absl::MutexLock lock(&mutex_);
   return now_;
diff --git a/internal/test/fake_clock.h b/internal/test/fake_clock.h
index 7cef161a..8c077e18 100644
--- a/internal/test/fake_clock.h
+++ b/internal/test/fake_clock.h
@@ -33,6 +33,7 @@ class FakeClock : public Clock {
   FakeClock() { now_ = absl::Now(); }
   FakeClock(FakeClock&&) = default;
   FakeClock& operator=(FakeClock&&) = default;
+  ~FakeClock() override ABSL_LOCKS_EXCLUDED(mutex_);
 
   absl::Time Now() const override;