diff --git a/setup.sh b/setup.sh
index 3e76218..b63abf8 100755
--- a/setup.sh
+++ b/setup.sh
@@ -21,12 +21,12 @@ unset md0pwd
 chroot=/mnt/md0-unlocked
 
 # root device
-mkfs.btrfs /dev/mapper/md0-unlocked
+mkfs.btrfs -f /dev/mapper/md0-unlocked
 mkdir /mnt/md0-unlocked
 mount /dev/mapper/md0-unlocked /mnt/md0-unlocked
 
 # boot device
-mkfs.btrfs /dev/md1
+mkfs.btrfs -f /dev/md1
 mkdir "$chroot/boot"
 mount /dev/md1 "$chroot/boot"