diff --git a/gomod_test.go b/gomod_test.go
new file mode 100644
index 000000000..f984b5d6f
--- /dev/null
+++ b/gomod_test.go
@@ -0,0 +1,25 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+package tailscaleroot
+
+import (
+	"os"
+	"testing"
+
+	"golang.org/x/mod/modfile"
+)
+
+func TestGoMod(t *testing.T) {
+	goMod, err := os.ReadFile("go.mod")
+	if err != nil {
+		t.Fatal(err)
+	}
+	f, err := modfile.Parse("go.mod", goMod, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(f.Replace) > 0 {
+		t.Errorf("go.mod has %d replace directives; expect zero in this repo", len(f.Replace))
+	}
+}