diff --git a/.env.example b/.env.example
index d843ca2a..14173ee5 100644
--- a/.env.example
+++ b/.env.example
@@ -22,7 +22,7 @@ BACKEND_DOMAIN_NAME=backend.example.com
 
 # Obtain the following 2 values on the Pi Developer Portal (open develop.pi in the Pi Browser).
 
-# Domain validation key:
+# Domain validation key:https://minepi.com/validation-key.txt
 DOMAIN_VALIDATION_KEY=todo_developer_portal
 # Pi Platform API Key:
 PI_API_KEY=todo_developer_portal