diff --git a/docs/api/v1.18.md b/docs/api/v1.18.md
index 513415fd7a..3b811c1515 100644
--- a/docs/api/v1.18.md
+++ b/docs/api/v1.18.md
@@ -21,8 +21,8 @@ redirect_from:
  - The daemon listens on `unix:///var/run/docker.sock` but you can
    [Bind Docker to another host/port or a Unix socket](../reference/commandline/dockerd.md#bind-docker-to-another-host-port-or-a-unix-socket).
  - The API tends to be REST, but for some complex commands, like `attach`
-   or `pull`, the HTTP connection is hijacked to transport `STDOUT`,
-   `STDIN` and `STDERR`.
+   or `pull`, the HTTP connection is hijacked to transport `stdout`,
+   `stdin` and `stderr`.
 
 ## 2. Endpoints