diff --git a/olm/olm.go b/olm/olm.go
index 5943456..0e622ee 100644
--- a/olm/olm.go
+++ b/olm/olm.go
@@ -56,6 +56,8 @@ type Config struct {
 	Version string
 	OrgID   string
 	// DoNotCreateNewClient bool
+
+	FileDescriptorTun uint32
 }
 
 var (
@@ -366,16 +368,16 @@ func TunnelProcess(ctx context.Context, config Config, id string, secret string,
 		}
 
 		tdev, err = func() (tun.Device, error) {
-			if runtime.GOOS == "darwin" {
+			if config.FileDescriptorTun != 0 {
+				return createTUNFromFD(config.FileDescriptorTun, config.MTU)
+			}
+			if runtime.GOOS == "darwin" { // this is if we dont pass a fd
 				interfaceName, err := findUnusedUTUN()
 				if err != nil {
 					return nil, err
 				}
 				return tun.CreateTUN(interfaceName, config.MTU)
 			}
-			if tunFdStr := os.Getenv(ENV_WG_TUN_FD); tunFdStr != "" {
-				return createTUNFromFD(tunFdStr, config.MTU)
-			}
 			return tun.CreateTUN(interfaceName, config.MTU)
 		}()
 
diff --git a/olm/unix.go b/olm/unix.go
index 4d8e3b6..5f5cf0e 100644
--- a/olm/unix.go
+++ b/olm/unix.go
@@ -5,25 +5,19 @@ package olm
 import (
 	"net"
 	"os"
-	"strconv"
 
 	"golang.org/x/sys/unix"
 	"golang.zx2c4.com/wireguard/ipc"
 	"golang.zx2c4.com/wireguard/tun"
 )
 
-func createTUNFromFD(tunFdStr string, mtuInt int) (tun.Device, error) {
-	fd, err := strconv.ParseUint(tunFdStr, 10, 32)
+func createTUNFromFD(tunFd uint32, mtuInt int) (tun.Device, error) {
+	err := unix.SetNonblock(int(tunFd), true)
 	if err != nil {
 		return nil, err
 	}
 
-	err = unix.SetNonblock(int(fd), true)
-	if err != nil {
-		return nil, err
-	}
-
-	file := os.NewFile(uintptr(fd), "")
+	file := os.NewFile(uintptr(tunFd), "")
 	return tun.CreateTUNFromFile(file, mtuInt)
 }
 func uapiOpen(interfaceName string) (*os.File, error) {