diff --git a/src/vnet/devices/tap/tap.c b/src/vnet/devices/tap/tap.c
index 7c8a9b0..b7ccba9 100644
--- a/src/vnet/devices/tap/tap.c
+++ b/src/vnet/devices/tap/tap.c
@@ -694,7 +694,7 @@
     {
       hw->min_frame_size = TUN_MIN_PACKET_BYTES;
       vnet_hw_interface_set_mtu (
-	vnm, hw->sw_if_index,
+	vnm, hw->hw_if_index,
 	args->host_mtu_size ? args->host_mtu_size : TUN_DEFAULT_PACKET_BYTES);
     }