diff --git a/test/e2e/framework/test_context.go b/test/e2e/framework/test_context.go
index a10dc823b5..7dad329114 100644
--- a/test/e2e/framework/test_context.go
+++ b/test/e2e/framework/test_context.go
@@ -252,8 +252,8 @@ func RegisterClusterFlags() {
 	flag.StringVar(&TestContext.KubectlPath, "kubectl-path", "kubectl", "The kubectl binary to use. For development, you might use 'cluster/kubectl.sh' here.")
 	flag.StringVar(&TestContext.OutputDir, "e2e-output-dir", "/tmp", "Output directory for interesting/useful test data, like performance data, benchmarks, and other metrics.")
 	flag.StringVar(&TestContext.Prefix, "prefix", "e2e", "A prefix to be added to cloud resources created during testing.")
-	flag.StringVar(&TestContext.MasterOSDistro, "master-os-distro", "debian", "The OS distribution of cluster master (debian, trusty, or coreos).")
-	flag.StringVar(&TestContext.NodeOSDistro, "node-os-distro", "debian", "The OS distribution of cluster VM instances (debian, trusty, or coreos).")
+	flag.StringVar(&TestContext.MasterOSDistro, "master-os-distro", "debian", "The OS distribution of cluster master (debian, ubuntu, gci, coreos, or custom).")
+	flag.StringVar(&TestContext.NodeOSDistro, "node-os-distro", "debian", "The OS distribution of cluster VM instances (debian, ubuntu, gci, coreos, or custom).")
 	flag.StringVar(&TestContext.ClusterMonitoringMode, "cluster-monitoring-mode", "standalone", "The monitoring solution that is used in the cluster.")
 	flag.BoolVar(&TestContext.EnablePrometheusMonitoring, "prometheus-monitoring", false, "Separate Prometheus monitoring deployed in cluster.")