Openstack CLI tool --prefix-length 27 does not work for Subnet creation

Issue

openstack subnet create --subnet-pool default --prefix-length 27 --network default default`

Does not create a network with a /27 CIDR.

$ openstack subnet create --subnet-pool default --prefix-length 27 --network default default
+-------------------+--------------------------------------+
| Field             | Value                                |
+-------------------+--------------------------------------+
| allocation_pools  | 192.168.0.2-192.168.0.14         |
| cidr              | 192.168.0.0/28                     |
| created_at        | 2018-10-22T01:30:38Z                 |
| description       |                                      |
| dns_nameservers   |                                      |
| enable_dhcp       | True                                 |
| gateway_ip        | 192.168.0.1                        |
| host_routes       |                                      |
| id                | c437f445-b319-4ee7-b518-293ffa294871 |
| ip_version        | 4                                    |
| ipv6_address_mode | None                                 |
| ipv6_ra_mode      | None                                 |
| name              | default                              |
| network_id        | 15e872f2-a2c9-4431-fede-e7e2399e359d |
| project_id        | 063b25ed7c094053be7a64c4f3caace0     |
| revision_number   | 0                                    |
| segment_id        | None                                 |
| service_types     |                                      |
| subnetpool_id     | 6b7e7e2a-8bc3-4214-bd91-317a12556ef9 |
| tags              |                                      |
| updated_at        | 2018-10-22T01:30:38Z                 |
+-------------------+--------------------------------------+