diff --git a/docs/environment-variables.md b/docs/environment-variables.md
index a1c105aa..09d5654b 100644
--- a/docs/environment-variables.md
+++ b/docs/environment-variables.md
@@ -10,6 +10,7 @@ Following environment variables are set into sites volume as `common_site_config
 - `REDIS_QUEUE`: Redis queue host, domain name or ip address.
 - `REDIS_SOCKETIO`: Redis queue host, domain name or ip address.
 - `SOCKETIO_PORT: `: Port on which the SocketIO should start.
+- `WORKER_CLASS`: Optionally set gunicorn worker-class. Supports gevent only, defaults to gthread.
 
 ### frappe-nginx and erpnext-nginx