diff --git a/util/racebuild/off.go b/util/racebuild/off.go
new file mode 100644
index 000000000..37f0f7cf1
--- /dev/null
+++ b/util/racebuild/off.go
@@ -0,0 +1,9 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !race
+
+package racebuild
+
+const On = false
diff --git a/util/racebuild/on.go b/util/racebuild/on.go
new file mode 100644
index 000000000..b318aa1b3
--- /dev/null
+++ b/util/racebuild/on.go
@@ -0,0 +1,9 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build race
+
+package racebuild
+
+const On = true
diff --git a/util/racebuild/racebuild.go b/util/racebuild/racebuild.go
new file mode 100644
index 000000000..30aad83e9
--- /dev/null
+++ b/util/racebuild/racebuild.go
@@ -0,0 +1,7 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package racebuild exports a constant about whether the current binary
+// was built with the race detector.
+package racebuild