diff --git a/tun/tun_netbsd.go b/tun/tun_netbsd.go
index 1fb7d5c..cc2004a 100644
--- a/tun/tun_netbsd.go
+++ b/tun/tun_netbsd.go
@@ -11,6 +11,7 @@ import (
 	"io/ioutil"
 	"net"
 	"os"
+    "sync"
 	"syscall"
 	"unsafe"