diff --git a/docs/reference/commandline/dockerd.md b/docs/reference/commandline/dockerd.md
index e530a4478e..213f38758c 100644
--- a/docs/reference/commandline/dockerd.md
+++ b/docs/reference/commandline/dockerd.md
@@ -191,7 +191,10 @@ $ docker -H ssh://example.com ps
 ```
 
 To use SSH connection, you need to set up `ssh` so that it can reach the
-remote host with public key authentication.
+remote host with public key authentication. Password authentication is not
+supported. If your key is protected with passphrase, you need to set up
+`ssh-agent`.
+
 Also, you need to have `docker` binary 18.09 or later on the daemon host.
 
 #### Bind Docker to another host/port or a Unix socket