diff --git a/locals.tf b/locals.tf
index 5520b6f..3590c2e 100644
--- a/locals.tf
+++ b/locals.tf
@@ -57,6 +57,7 @@ locals {
       runners_enable_monitoring             = var.runners_enable_monitoring
       runners_network                       = var.network
       runners_subnetwork                    = var.subnetwork
+      runners_docker_machine_image          = var.runner_machine_image
   })
 
   template_shutdown_script = templatefile("${path.module}/templates/shutdown-script.sh.tpl", {
@@ -116,3 +117,4 @@ locals {
     }
   )
 }
+
diff --git a/templates/startup-script.sh.tpl b/templates/startup-script.sh.tpl
index a5b60de..cd48959 100644
--- a/templates/startup-script.sh.tpl
+++ b/templates/startup-script.sh.tpl
@@ -63,7 +63,7 @@ else
   # See: https://github.com/docker/machine/issues/3845#issuecomment-280389178
   export USER=root
   export HOME=/root
-  suffix="$(< /dev/urandom tr -dc _a-z-0-9 | head -c6)"
+  suffix="$(< /dev/urandom tr -dc a-z-0-9 | head -c6)"
   dummymachine="${prefix}-gitlab-runner-dummy-machine-$suffix"
   echo "Verifying docker-machine and generating SSH keys ahead of time."
   docker-machine create --driver google \
@@ -79,6 +79,9 @@ else
       %{~ if runners_subnetwork != "" ~}
       --google-subnetwork ${runners_subnetwork} \
       %{~ endif ~}
+      %{~ if runners_docker_machine_image != "" ~}
+      --google-machine-image ${runners_docker_machine_image} \
+      %{~ endif ~}
       $dummymachine
   docker-machine rm -y $dummymachine
   unset HOME
@@ -136,3 +139,4 @@ ${post_install}
 
 service gitlab-runner restart
 chkconfig gitlab-runner on
+
diff --git a/variables.tf b/variables.tf
index cca96bb..5fd6148 100644
--- a/variables.tf
+++ b/variables.tf
@@ -82,7 +82,7 @@ variable "docker_machine_preemptible" {
 variable "runner_machine_image" {
   description = "A GCP custom image to use for spinning up runners when using docker-machine"
   type        = string
-  default     = "ubuntu-os-cloud/global/images/ubuntu-2004-focal-v20220419"
+  default     = "cos-cloud/global/images/family/cos-97-lts"
 }
 
 variable "docker_machine_disk_type" {