diff --git a/cluster/kubemark/config-default.sh b/cluster/kubemark/config-default.sh
index d4c2a195dea..c6fd520252d 100644
--- a/cluster/kubemark/config-default.sh
+++ b/cluster/kubemark/config-default.sh
@@ -24,8 +24,10 @@ source "${KUBE_ROOT}/cluster/gce/config-common.sh"
 GCLOUD=gcloud
 ZONE=${KUBE_GCE_ZONE:-us-central1-b}
 REGION=${ZONE%-*}
-NUM_NODES=${NUM_NODES:-100}
-MASTER_SIZE=${MASTER_SIZE:-n1-standard-$(get-master-size)}
+# KUBEMARK_NUM_NODES overrides NUM_NODES if set
+NUM_NODES=${KUBEMARK_NUM_NODES:-${NUM_NODES:-100}}
+# KUBEMARK_MASTER_SIZE overrides MASTER_SIZE if set
+MASTER_SIZE=${KUBEMARK_MASTER_SIZE:-${MASTER_SIZE:-n1-standard-$(get-master-size)}}
 MASTER_DISK_TYPE=pd-ssd
 MASTER_DISK_SIZE=${MASTER_DISK_SIZE:-20GB}
 MASTER_ROOT_DISK_SIZE=${KUBEMARK_MASTER_ROOT_DISK_SIZE:-10GB}