diff --git a/hco/env/ctrl3-wrkr4-ceph.yaml b/hco/env/ctrl3-wrkr4-ceph.yaml
index eba05be..abb77e4 100644
--- a/hco/env/ctrl3-wrkr4-ceph.yaml
+++ b/hco/env/ctrl3-wrkr4-ceph.yaml
@@ -10,6 +10,9 @@
   public_net_id: public
   cluster_public_key: ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQCp0evjOaK8c8SKYK4r2+0BN7g+8YSvQ2n8nFgOURCyvkJqOHi1qPGZmuN0CclYVdVuZiXbWw3VxRbSW3EH736VzgY1U0JmoTiSamzLHaWsXvEIW8VCi7boli539QJP0ikJiBaNAgZILyCrVPN+A6mfqtacs1KXdZ0zlMq1BPtFciR1JTCRcVs5vP2Wwz5QtY2jMIh3aiwkePjMTQPcfmh1TkOlxYu5IbQyZ3G1ahA0mNKI9a0dtF282av/F6pwB/N1R1nEZ/9VtcN2I1mf1NW/tTHEEcTzXYo1R/8K9vlqAN8QvvGLZtZduGviNVNoNWvoxaXxDt8CPv2B2NCdQFZp
   worker_metadata: {"labels": {"role":"ceph-osd-node"}}
+  # hardware_metadata which is used for Ceph requires flavor with
+  # ephemeral storage because it is used for Ceph bluestore.
+  workers_flavor: 'mosk.l.control.ephemeral'
   hardware_metadata: |
     '00:00:00:00:00:00':
       write_files: