Index: sys/net/if_ethersubr.c
===================================================================
--- sys/net/if_ethersubr.c	(revision 363232)
+++ sys/net/if_ethersubr.c	(working copy)
@@ -927,8 +927,8 @@
 
 	ifp->if_addrlen = ETHER_ADDR_LEN;
 	ifp->if_hdrlen = ETHER_HDR_LEN;
+	ifp->if_mtu = ETHERMTU;
 	if_attach(ifp);
-	ifp->if_mtu = ETHERMTU;
 	ifp->if_output = ether_output;
 	ifp->if_input = ether_input;
 	ifp->if_resolvemulti = ether_resolvemulti;