diff --git a/docs/getting-started-guides/rkt/README.md b/docs/getting-started-guides/rkt/README.md
index 9bf573e5f26..344fee8db42 100644
--- a/docs/getting-started-guides/rkt/README.md
+++ b/docs/getting-started-guides/rkt/README.md
@@ -46,6 +46,12 @@ To use rkt as the container runtime for your CoreOS cluster on GCE, you need to
 $ export KUBE_OS_DISTRIBUTION=coreos
 $ export KUBE_GCE_MINION_IMAGE=<image_id>
 $ export KUBE_GCE_MINION_PROJECT=coreos-cloud
+$ export KUBE_CONTAINER_RUNTIME=rkt
+```
+
+You can optionally choose the version of rkt used by setting `KUBE_RKT_VERSION`:
+```shell
+export KUBE_RKT_VERSION=0.5.6
 ```
 
 Then you can launch the cluster by: