(update-uri (uri-reference "")
            scheme: 'http
            port: (server-port)
            host: (or (server-bind-address)
                      "0.0.0.0"))

;; versus

(make-uri scheme: 'http
          port: (server-port)
          host: (or (server-bind-address)
                    "0.0.0.0"))