Numeric Domain Names get treated as Domain ID

We are using OpenStack Domains and every client gets a user with a manager role to manage users and projects within its domain.
The manager user has a manager role assigned on its domain.

When i want to create a project i observed the following behavior in the client:

Working as expected when using the Domain ID on the project create command:

openstack --os-username 1234-manager \
          --os-password removed \
          --os-auth-url removed \
          --os-user-domain-name 1234 \
          --os-domain-name 1234 \
          --os-auth-type password \
project create test123 --domain 025a1b9727554eb78aaa8bcb4b3200d5
+-------------+----------------------------------+
| Field | Value |
+-------------+----------------------------------+
| description | |
| domain_id | 025a1b9727554eb78aaa8bcb4b3200d5 |
| enabled | True |
| id | 97bc5fb9eb4241bdb7c97283af7b1ae8 |
| is_domain | False |
| name | test123 |
| options | {} |
| parent_id | 025a1b9727554eb78aaa8bcb4b3200d5 |
| tags | [] |
+-------------+----------------------------------+

But when using the Domain Name that is numeric in this Case it fails because it treats the domain name as the Domain ID:

openstack --os-username 1234-manager \
          --os-password removed \
          --os-auth-url removed \
          --os-user-domain-name 1234 \
          --os-domain-name 1234 \
          --os-auth-type password \
project create test123 --domain 1234
You are not authorized to perform the requested action: identity:create_project. (HTTP 403) (Request-ID: req-000cb034-ac70-4ab1-849e-0de3888fba09)

The resulting request is:

REQ: curl -g -i -X POST https://<keystone-endpoint>/v3/projects \
  -H "Accept: application/json" \
  -H "Content-Type: application/json" \
  -H "User-Agent: python-keystoneclient" \
  -H "X-Auth-Token: <redacted>" \
  -d '{"project": {"domain_id": "1234", "name": "test123", "enabled": true, "options": {}, "tags": []}}'

I tested this on Version: openstack 8.1.0
Adding a single non-numeric char to the domain Name fixes the issue because its not treated as an id but it seems like a bug to me.