KeepInventory on the classic pack

Hey im trying to use the comand in the server console

/gamerule keepInventory true

but it doesnt work in the classic pack(industrial craft buildcraft gravekeep... etc) on my server in aternos, someone can tell me what i have to do, i dont like the gravekeep mod instaled in this modpack

thanks man, but it dosnt works, maybe the problem is the gravestone mod? if it is, there is a way to disable that mode? thanks

it works when i set the command, but after some time the gravestone still take my itens