diff --git a/website/docs/source/v2/docker/configuration.html.md b/website/docs/source/v2/docker/configuration.html.md
index b2c146bac..6b2ca933a 100644
--- a/website/docs/source/v2/docker/configuration.html.md
+++ b/website/docs/source/v2/docker/configuration.html.md
@@ -18,6 +18,9 @@ you may set. A complete reference is shown below.
 
 ### Optional
 
+  * `build_args` (array of strings) - Extra arguments to pass to
+      `docker build` when `build_dir` is in use.
+
   * `cmd` (array of strings) - Custom command to run on the container.
     Example: `["ls", "/app"]`.