diff --git a/contrib/terraform/openstack/README.md b/contrib/terraform/openstack/README.md
index 7b7e9e1ce..76741b31c 100644
--- a/contrib/terraform/openstack/README.md
+++ b/contrib/terraform/openstack/README.md
@@ -273,6 +273,7 @@ For your cluster, edit `inventory/$CLUSTER/cluster.tfvars`.
 |`wait_for_floatingip` | Let Terraform poll the instance until the floating IP has been associated, `false` by default. |
 |`node_root_volume_size_in_gb` | Size of the root volume for nodes, 0 to use ephemeral storage |
 |`master_root_volume_size_in_gb` | Size of the root volume for masters, 0 to use ephemeral storage |
+|`master_volume_type` | Volume type of the root volume for control_plane, 'Default' by default |
 |`gfs_root_volume_size_in_gb` | Size of the root volume for gluster, 0 to use ephemeral storage |
 |`etcd_root_volume_size_in_gb` | Size of the root volume for etcd nodes, 0 to use ephemeral storage |
 |`bastion_root_volume_size_in_gb` | Size of the root volume for bastions, 0 to use ephemeral storage |