diff --git a/api/README.md b/api/README.md
index f136c3433a..381f19881f 100644
--- a/api/README.md
+++ b/api/README.md
@@ -37,6 +37,6 @@ There is hopefully enough example material in the file for you to copy a similar
 
 When you make edits to `swagger.yaml`, you may want to check the generated API documentation to ensure it renders correctly.
 
-Run `make swagger-docs` and a preview will be running at `http://localhost`. Some of the styling may be incorrect, but you'll be able to ensure that it is generating the correct documentation.
+Run `make swagger-docs` and a preview will be running at `http://localhost:9000`. Some of the styling may be incorrect, but you'll be able to ensure that it is generating the correct documentation.
 
 The production documentation is generated by vendoring `swagger.yaml` into [docker/docker.github.io](https://github.com/docker/docker.github.io).