How to change the "Recovery HD" partition to type "Apple_Boot"? Typing in the terminal diskutil list gives me this...

/dev/disk0 (internal, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *500.1 GB   disk0
   1:                        EFI EFI                     209.7 MB   disk0s1
   2:                  Apple_HFS Macintosh HD            499.1 GB   disk0s2
   3:                  Apple_HFS Recovery HD             629.1 MB   disk0s3


I try to change disk0s3 to type "Apple_Boot", by using...

sudo asr adjust --target /dev/disk0s3 -settype "Apple_Boot"


But I keep getting the error...

asr: Volume adjustment failed: Operation not permitted




The partition isn't mounted. I have also tried the command as superuser.
At first:

umount -f "/Volumes/Recovery HD"


Then:

sudo asr adjust --target /dev/disk0s3 -settype "Apple_Boot"