zfs send : internal error: Invalid argument. Abort.

Hello,
I'm trying to send a replication snapshot over SSH to another host.
Am I doing something wrong?

root@s11-desktop:~# zfs list -r -t snap rpool
NAME                                                                    USED  AVAIL  REFER  MOUNTPOINT
...
rpool/export/home/user1@backup-1                                       7.07M      -  3.11G  -
rpool/export/home/user1/Application@backup-1                               0      -  6.32M  -
rpool/export/home/user1/Backup@backup-1                                    0      -    31K  -
rpool/export/home/user1/Database@backup-1                                  0      -  3.17G  -
rpool/export/home/user1/Notes@backup-1                                     0      -  3.44G  -   <== The original dataset is encrypted, so the snapshot I believe!
rpool/export/home/user1/Projects@backup-1                                  0      -   612K  -           But then, wait a minute, can correctly take a snapshot