An invalid enumeration value M0 was specified

Hi

I’m trying to create an M0 cluster using terraform

resource "mongodbatlas_advanced_cluster" "plan" {
  project_id   = var.atlas_project_id
  name         = var.service_name
  cluster_type = "SHARED"
  mongo_db_major_version = "7.0"

  replication_specs {
    region_configs {
      electable_specs {
        instance_size = "M0"
      }
      provider_name = "AWS"
      priority      = 7
      region_name   = "US_EAST_1"
    }
  }
}

But I’m getting the following error

mongodbatlas_advanced_cluster.plan: Creating...
╷
│ Error: error creating advanced cluster: https://cloud.mongodb.com/api/atlas/v2/groups/66e9d23a696bf219fa7e72b0/clusters POST: HTTP 400 Bad Request (Error code: "INVALID_ENUM_VALUE") Detail: An invalid enumeration value M0 was specified. Reason: Bad Request. Params: [M0]

What am I missing?

Thanks