Slow booting with raid-1 encrypted filesystems

On my system I have two filesystems that are in encrypted Raid-1 partitions. I have the partitions in crypttab using the UUIDs of the partitions. It seems that cryptsetup is being run before mdadm assembles the raid units. This times out after a few minutes. Then, later in the boot process, mdmonitor runs, assembles the raid device, and then something runs cryptsetup. Boot succeeds (after I added nofail as an option in fstab), but there is a period of several minutes where cryptsetup is waiting for devices to come online that don’t and won’t. Is there a way to shortcircuit that?