diff --git a/cmd/kubeadm/app/phases/bootstraptoken/clusterinfo/clusterinfo.go b/cmd/kubeadm/app/phases/bootstraptoken/clusterinfo/clusterinfo.go
index 5f6c27e3d8c..80658726d40 100644
--- a/cmd/kubeadm/app/phases/bootstraptoken/clusterinfo/clusterinfo.go
+++ b/cmd/kubeadm/app/phases/bootstraptoken/clusterinfo/clusterinfo.go
@@ -47,6 +47,9 @@ func CreateBootstrapConfigMapIfNotExists(client clientset.Interface, file string
 	if err != nil {
 		return errors.Wrap(err, "failed to load admin kubeconfig")
 	}
+	if err = clientcmdapi.FlattenConfig(adminConfig); err != nil {
+		return err
+	}
 
 	adminCluster := adminConfig.Contexts[adminConfig.CurrentContext].Cluster
 	// Copy the cluster from admin.conf to the bootstrap kubeconfig, contains the CA cert and the server URL