diff --git a/cluster/common.sh b/cluster/common.sh
index 0f5d8209f58..2a0812829d7 100755
--- a/cluster/common.sh
+++ b/cluster/common.sh
@@ -517,7 +517,7 @@ function build-kube-env {
 
   local server_binary_tar_url=$SERVER_BINARY_TAR_URL
   local salt_tar_url=$SALT_TAR_URL
-  local kube_manifests_tar_url=$KUBE_MANIFESTS_TAR_URL
+  local kube_manifests_tar_url="${KUBE_MANIFESTS_TAR_URL:-}"
   if [[ "${master}" == "true" && "${MASTER_OS_DISTRIBUTION}" == "coreos" ]] || \
      [[ "${master}" == "false" && "${NODE_OS_DISTRIBUTION}" == "coreos" ]] ; then
     # TODO: Support fallback .tar.gz settings on CoreOS