Memcached commands noreply option error

No reply not appearing to work fine. Example:

echo -e "delete a noreply\r" | nc localhost 11211
produces
SERVER_ERROR java.lang.NullPointerException

Other examples:
$ echo -e "set a 0 0 1\r\na\r\ndelete a\r\ndelete a\r\ndelete a\r\ndelete a\r\n" | nc localhost 11211
STORED
DELETED
NOT_FOUND
NOT_FOUND
NOT_FOUND
$ echo -e "set a 0 0 1 noreply\r\na\r\ndelete a\r\ndelete a\r\ndelete a\r\ndelete a\r\n" | nc localhost 11211
$