diff --git a/sys/dev/virtio/network/if_vtnet.c b/sys/dev/virtio/network/if_vtnet.c
--- a/sys/dev/virtio/network/if_vtnet.c
+++ b/sys/dev/virtio/network/if_vtnet.c
@@ -1299,8 +1299,11 @@
 		if (sc->vtnet_flags & VTNET_FLAG_CTRL_RX)
 			vtnet_rx_filter(sc);
 		else {
-			if ((if_getflags(ifp) ^ sc->vtnet_if_flags) & IFF_ALLMULTI)
-				return (ENOTSUP);
+			/*
+			 * We don't support filtering out multicast, so
+			 * ALLMULTI is always set.
+			 */
+			if_setflagbits(ifp, IFF_ALLMULTI, 0);
 			if_setflagbits(ifp, IFF_PROMISC, 0);
 		}
 	}