diff --git a/README.md b/README.md
index 941ffff7..0c736d43 100644
--- a/README.md
+++ b/README.md
@@ -8,6 +8,25 @@ Usage
 
 See on [tmate.io](http://tmate.io/).
 
+Docker image
+-----------
+
+A docker image is provided:
+[`tmate/tmate-ssh-server`](https://hub.docker.com/r/tmate/tmate-ssh-server)
+
+The following environment variables are used to configure the server:
+
+* `SSH_KEYS_PATH` (mandatory): The path where the ssh keys are located.
+* `HAS_WEBSOCKET`: set to `1` if the tmate-websocket server exists (for HTML5
+  clients).
+* `USE_PROXY_PROTOCOL`: set to `1` if the ssh server is behind a load balancer
+  that uses the [proxy protocol](http://www.haproxy.org/download/1.8/doc/proxy-protocol.txt) enabled.
+  This is useful to get client real IPs.
+* `SSH_HOSTNAME`: configures the SSH hostname to advertise to tmate hosts.
+* `SSH_PORT_LISTEN`: port on which the SSH server should listen on.
+* `SSH_PORT_ADVERTISE`: configures the SSH port to advertise to tmate hosts.
+  Defaults to `SSH_PORT_LISTEN`.
+
 License
 --------
 
diff --git a/docker-entrypoint.sh b/docker-entrypoint.sh
index 2f1f7c1e..85f8e738 100755
--- a/docker-entrypoint.sh
+++ b/docker-entrypoint.sh
@@ -15,5 +15,6 @@ fi
 
 SSH_PORT_LISTEN=${SSH_PORT_LISTEN:-2200}
 SSH_PORT_ADVERTIZE=${SSH_PORT_ADVERTIZE:-${SSH_PORT_LISTEN}}
+SSH_PORT_ADVERTISE=${SSH_PORT_ADVERTISE:-${SSH_PORT_ADVERTIZE}}
 
-exec tmate-ssh-server -p ${SSH_PORT_LISTEN} -q ${SSH_PORT_ADVERTIZE} -k ${SSH_KEYS_PATH} "$@"
+exec tmate-ssh-server -p ${SSH_PORT_LISTEN} -q ${SSH_PORT_ADVERTISE} -k ${SSH_KEYS_PATH} "$@"