WOL on em0 (enable wol_magic by default)

Hello,

I recognized that the if_em FreeBSD driver doesn't enable wol_magic by 
default.
Recently I found out that interrupting the boot process of a ESX machine 
would lead to a non-ethernet-wakable server. Only after booting and 
shutting down the ESX(i) the server woke up as expected.
Now I checked it with FreeSBD and after shutting down the server it 
doesn't respond to wol magic packets.
One has to set `ifconfig em0 wol_magic` for example. Then it worked, 
although the wol feature isn't reported by the interface:
em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
         options=9b<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,VLAN_HWCSUM>

Now comes the annoying part: It works only _sometimes_
Haven't found any rule yet.
Maybe someone else can shade light on this mystic WOL behaviour (Jack?)

Thanks in advance,

-Harry