Before this patch:

root@57:~/iftop-1.0pre4# ./iftop 

interface: eth0

IP address is: 192.168.1.57

MAC address is: ffffffbc:ffffffee:7b:ffffffdb:0b:ffffffd4

With this patch

root@57:~/iftop-1.0pre4# ./iftop 

interface: eth0

IP address is: 192.168.1.57

MAC address is: bc:ee:7b:db:0b:d4