Terraform Vault Provider Namespace is not working as a Provider Alias

Problem

Using the following Vault provider block to define an aliased provider for the namespace produces an error: 

provider "vault" {
  alias = "admin/dev"
  namespace = "admin/dev"
}


│ Error: error reading from Vault: Error making API request.
│
│ Namespace: admin/
│ URL: GET https://x.x.x.x
│ Code: 400. Errors:
│
│ * "/" is not allowed in namespace names

Cause

The argument alias does not allow the / character in a valid alias name.

Solutions

The following Terraform code works successfully by replacing the / character with a - character:

provider "vault" {
  alias = "admin-dev"
  namespace = "admin/dev"
}

Additional Information

Provider Aliases