diff --git a/device/tun/tun.go b/device/tun/tun.go
index d617d70..53dfa8d 100755
--- a/device/tun/tun.go
+++ b/device/tun/tun.go
@@ -5,10 +5,10 @@ import (
 	"github.com/xjasonlyu/tun2socks/device"
 )
 
-const driverType = "tun"
+const Driver = "tun"
 
 func (t *TUN) Type() string {
-	return driverType
+	return Driver
 }
 
 var _ device.Device = (*TUN)(nil)
diff --git a/engine/parse.go b/engine/parse.go
index 8fd095a..c7f4291 100644
--- a/engine/parse.go
+++ b/engine/parse.go
@@ -12,9 +12,8 @@ import (
 )
 
 func parseDevice(s string, mtu uint32) (device.Device, error) {
-	const defaultDriver = "tun"
 	if !strings.Contains(s, "://") {
-		s = defaultDriver + "://" + s
+		s = tun.Driver + "://" + s /* default driver */
 	}
 
 	u, err := url.Parse(s)
@@ -26,7 +25,7 @@ func parseDevice(s string, mtu uint32) (device.Device, error) {
 	driver := strings.ToLower(u.Scheme)
 
 	switch driver {
-	case "tun":
+	case tun.Driver:
 		return tun.Open(tun.WithName(name), tun.WithMTU(mtu))
 	default:
 		return nil, fmt.Errorf("unsupported driver: %s", driver)