diff --git a/README.md b/README.md
index 66d3658..bc62917 100644
--- a/README.md
+++ b/README.md
@@ -22,6 +22,7 @@ Set `PUBLIC_MQTT_BROKER_WS_URL` environment variable for MQTT broker. Since brow
 cp .env.example .env
 
 # edit .env in favorite text editor
+# PUBLIC_MQTT_BROKER_WS_URL=ws://test.mosquitto.org
 ```
 
 # Run