Cannot contain self-reference in terraform cloudflare page rule

Question

I want to create a pagerule to ensure all the incoming http traffic will be converted to https

Here is my rule:

resource "cloudflare_page_rule" "https-only" {
    zone = "${var.domain}"
    domain = "${var.domain}"
    target = "http://*${self.domain}/*"
    priority = 1

    actions = {
        always_use_https = true
    }
}

The target line is based on the example provided by terraform

However when I run the terraform file, I get this error

Error: resource 'cloudflare_page_rule.https-only' config: cannot contain self-reference self.domain

Is the example no longer valid? If so, what is the proper syntax?