diff --git a/ci/pipelines/builder.yml b/ci/pipelines/builder.yml
index 26ea516347..5a5a3161dd 100644
--- a/ci/pipelines/builder.yml
+++ b/ci/pipelines/builder.yml
@@ -248,7 +248,7 @@ jobs:
     params:
       OPERATING_SYSTEM_NAME: ubuntu
       OPERATING_SYSTEM_VERSION: (@= data.values.stemcell_details.os_short_name @)
-      UBUNTU_DEBOOTSTRAP_MIRROR: http://gce.archive.ubuntu.com/ubuntu # Ubuntu's GCP-internal mirror, must change if we change Concourse IaaS!
+      UBUNTU_DEBOOTSTRAP_MIRROR: http://gce.archive.ubuntu.com/ubuntu #! Ubuntu's GCP-internal mirror, must change if we change Concourse IaaS!
     privileged: true
     vars:
       image_os_tag: (@= data.values.stemcell_details.os_short_name @)