diff --git a/cluster/gce/gci/configure-helper.sh b/cluster/gce/gci/configure-helper.sh
index 54b025b1ed8..00b11b495ec 100644
--- a/cluster/gce/gci/configure-helper.sh
+++ b/cluster/gce/gci/configure-helper.sh
@@ -2050,7 +2050,7 @@ fi
 
 override-kubectl
 # Run the containerized mounter once to pre-cache the container image.
-if [[ "${CONTAINER_RUNTIME:-}" == "docker" ]]; then
+if [[ "${CONTAINER_RUNTIME:-docker}" == "docker" ]]; then
   assemble-docker-flags
 fi
 start-kubelet