diff --git a/timer/api/BUILD.bazel b/timer/api/BUILD.bazel
index 29d52d03025f4..cf946f4a10a59 100644
--- a/timer/api/BUILD.bazel
+++ b/timer/api/BUILD.bazel
@@ -32,6 +32,7 @@ go_test(
     ],
     embed = [":api"],
     flaky = True,
+    race = "on",
     shard_count = 12,
     deps = [
         "//testkit/testsetup",
diff --git a/timer/api/mem_store.go b/timer/api/mem_store.go
index 2a82667a5164b..bf319eca03a27 100644
--- a/timer/api/mem_store.go
+++ b/timer/api/mem_store.go
@@ -98,6 +98,9 @@ func (s *memoryStoreCore) Create(_ context.Context, record *TimerRecord) (string
 }
 
 func (s *memoryStoreCore) List(_ context.Context, cond Cond) ([]*TimerRecord, error) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+
 	result := make([]*TimerRecord, 0, 1)
 	for _, ns := range s.namespaces {
 		for _, t := range ns {
diff --git a/timer/runtime/BUILD.bazel b/timer/runtime/BUILD.bazel
index 624359cbea9e0..b0f07bfd940d0 100644
--- a/timer/runtime/BUILD.bazel
+++ b/timer/runtime/BUILD.bazel
@@ -30,6 +30,7 @@ go_test(
     ],
     embed = [":runtime"],
     flaky = True,
+    race = "on",
     shard_count = 18,
     deps = [
         "//testkit/testsetup",