diff --git a/x-pack/plugins/fleet/README.md b/x-pack/plugins/fleet/README.md
index b1f52dbed9cfb..1b18b72647537 100644
--- a/x-pack/plugins/fleet/README.md
+++ b/x-pack/plugins/fleet/README.md
@@ -71,3 +71,9 @@ You need to have `docker` to run ingest manager api integration tests
    ```
    FLEET_PACKAGE_REGISTRY_PORT=12345 yarn test:ftr:runner --config x-pack/test/fleet_api_integration/config.ts --grep='fleet'
    ```
+
+**Note** you can also supply which docker image to use for the package registry via the `FLEET_PACKAGE_REGISTRY_DOCKER_IMAGE` env variable. For example,
+
+```
+FLEET_PACKAGE_REGISTRY_DOCKER_IMAGE='docker.elastic.co/package-registry/distribution:production' FLEET_PACKAGE_REGISTRY_PORT=12345 yarn test:ftr:runner
+```