diff --git a/deploy/prod.tag b/deploy/prod.tag
index e0594d0..4b17464 100644
--- a/deploy/prod.tag
+++ b/deploy/prod.tag
@@ -2,4 +2,5 @@
 # ~/containers/car-tracker/reconcile.sh. The value must be a full 40-character
 # commit SHA of a revision whose image has been pushed to the Gitea registry as
 # tonio/car-tracker:<sha>. To roll back, revert the commit that changed this file.
+# Lines beginning with # are ignored.
 2c58234fd9f360f262fde255fae5273ec8f57f6c