diff --git a/cluster/gce/configure-vm.sh b/cluster/gce/configure-vm.sh
index 9c83109543e..05349845b35 100755
--- a/cluster/gce/configure-vm.sh
+++ b/cluster/gce/configure-vm.sh
@@ -434,10 +434,10 @@ hairpin_mode: '$(echo "$HAIRPIN_MODE" | sed -e "s/'/''/g")'
 opencontrail_tag: '$(echo "$OPENCONTRAIL_TAG" | sed -e "s/'/''/g")'
 opencontrail_kubernetes_tag: '$(echo "$OPENCONTRAIL_KUBERNETES_TAG")'
 opencontrail_public_subnet: '$(echo "$OPENCONTRAIL_PUBLIC_SUBNET")'
-enable_manifest_url: '$(echo "$ENABLE_MANIFEST_URL" | sed -e "s/'/''/g")'
-manifest_url: '$(echo "$MANIFEST_URL" | sed -e "s/'/''/g")'
-manifest_url_header: '$(echo "$MANIFEST_URL_HEADER" | sed -e "s/'/''/g")'
-num_nodes: $(echo "${NUM_NODES}" | sed -e "s/'/''/g")
+enable_manifest_url: '$(echo "${ENABLE_MANIFEST_URL:-}" | sed -e "s/'/''/g")'
+manifest_url: '$(echo "${MANIFEST_URL:-}" | sed -e "s/'/''/g")'
+manifest_url_header: '$(echo "${MANIFEST_URL_HEADER:-}" | sed -e "s/'/''/g")'
+num_nodes: $(echo "${NUM_NODES:-}" | sed -e "s/'/''/g")
 e2e_storage_test_environment: '$(echo "$E2E_STORAGE_TEST_ENVIRONMENT" | sed -e "s/'/''/g")'
 EOF
     if [ -n "${KUBELET_PORT:-}" ]; then