supernetting with dhcp on asa

hi,

is it still impossible to set up dhcpd on a ASA 5520 with a network, say, 192.168.10.0/23? the interface *is* set on

the errormessage always says "no more than 256 addresses", whilst the cisco-knowledgebase is a bit unclear at this point.

thanx in advance for help!

greetings

lars maliwi