diff --git a/website/source/docs/commands/lock.html.markdown b/website/source/docs/commands/lock.html.markdown
index 06cac41926..5073ce22fd 100644
--- a/website/source/docs/commands/lock.html.markdown
+++ b/website/source/docs/commands/lock.html.markdown
@@ -60,5 +60,7 @@ The list of available flags are:
 
 * `-token` - ACL token to use. Defaults to that of agent.
 
+* `-pass-stdin` - Pass stdin to child process.
+
 * `-verbose` - Enables verbose output.