Ceph » rbd

I have the following snapshot under the namespace `ns1`:

ceph-dev:/ceph/build # bin/rbd info rbd/ns1/img1@img1_2019-09-19T21:32:47.161+01:00
2019-09-19T20:43:45.392+0000 7ff01bcacec0 -1 WARNING: all dangerous and experimental features are enabled.
2019-09-19T20:43:45.392+0000 7ff01bcacec0 -1 WARNING: all dangerous and experimental features are enabled.
2019-09-19T20:43:45.396+0000 7ff01bcacec0 -1 WARNING: all dangerous and experimental features are enabled.
rbd image 'img1':
    size 1 GiB in 256 objects
    order 22 (4 MiB objects)
    snapshot_count: 1
    id: 131a7b69432d
    block_name_prefix: rbd_data.131a7b69432d
    format: 2
    features: layering, exclusive-lock, object-map, fast-diff, deep-flatten
    op_features: 
    flags: 
    create_timestamp: Thu Sep 19 20:32:06 2019
    access_timestamp: Thu Sep 19 20:32:06 2019
    modify_timestamp: Thu Sep 19 20:32:06 2019
    protected: True

When I try to clone it, I get the following error:

ceph-dev:/ceph/build # bin/rbd clone rbd/ns1/img1@img1_2019-09-19T21:32:47.161+01:00 rbd/ns1/img2
2019-09-19T20:34:41.272+0000 7fb9d35dcec0 -1 WARNING: all dangerous and experimental features are enabled.
2019-09-19T20:34:41.272+0000 7fb9d35dcec0 -1 WARNING: all dangerous and experimental features are enabled.
2019-09-19T20:34:41.276+0000 7fb9d35dcec0 -1 WARNING: all dangerous and experimental features are enabled.
rbd: /ceph/src/cls/rbd/cls_rbd_client.cc:489: void librbd::cls_client::add_child(librados::v14_2_0::ObjectWriteOperation*, const cls::rbd::ParentImageSpec&, const string&): Assertion `pspec.pool_namespace.empty()' failed.
*** Caught signal (Aborted) **

<SEE FILE ATTACHED TO THIS ISSUE> 

Aborted (core dumped)