diff --git a/README.md b/README.md
index da8e151..234f13a 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,9 @@
 Terraform Provider Airflow
 ==========================
 
+[![terraformregistry](https://img.shields.io/badge/terraform-registry-blueviolet)](https://registry.terraform.io/providers/houqp/airflow)
 ![build](https://github.com/houqp/terraform-provider-airflow/workflows/build/badge.svg)
 
+
 Terraform provider for managing Airflow resources. See `examples` folder for
 documentations on how to configure and use this provider.
diff --git a/examples/variable/demo.tf b/examples/variable/demo.tf
index 5fa71e8..bc3de16 100644
--- a/examples/variable/demo.tf
+++ b/examples/variable/demo.tf
@@ -1,3 +1,12 @@
+terraform {
+  required_providers {
+    airflow = {
+      source  = "houqp/airflow"
+      version = "0.2.1"
+    }
+  }
+}
+
 provider "airflow" {
   base_endpoint = "http://localhost:28080/"
   username      = "test"