How to use bigger fields

[redeexpressos]

#[bitfield(u64)]
#[derive(PartialEq)]
pub struct Message {
    #[bits(8)]
    pub message_id: u8,
    #[bits(24)]
    pub time_of_reception: u32,
    #[bits(3456)]
    pub payload: [u8; 432],
}

if i remove (u64), throws unknown type.

How can I use something this crate for bigger fields?