diff --git a/prometheus/alertmanager/.dockerignore b/prometheus/alertmanager/.dockerignore
new file mode 100644
index 0000000..87ae095
--- /dev/null
+++ b/prometheus/alertmanager/.dockerignore
@@ -0,0 +1,2 @@
+README.md
+test/
diff --git a/prometheus/alertmanager/Containerfile b/prometheus/alertmanager/Containerfile
index e1319c1..4bcaa1a 100644
--- a/prometheus/alertmanager/Containerfile
+++ b/prometheus/alertmanager/Containerfile
@@ -1,5 +1,7 @@
-ARG CONTAINER_REGISTRY=docker.io
-FROM $CONTAINER_REGISTRY/ubuntu:noble-20241015 AS base
+# syntax=docker/dockerfile:1
+ARG BASE_IMAGE=docker.io/ubuntu:noble-20241015
+# hadolint ignore=DL3006
+FROM $BASE_IMAGE AS base
 
 ARG ALERTMANAGER_URL_AMD64
 ARG ALERTMANAGER_SHA256_AMD64
diff --git a/prometheus/alertmanager/docker-bake.hcl b/prometheus/alertmanager/docker-bake.hcl
index 0c8f3a5..e6b2114 100644
--- a/prometheus/alertmanager/docker-bake.hcl
+++ b/prometheus/alertmanager/docker-bake.hcl
@@ -1,15 +1,11 @@
-variable "IMAGE_NAME" {
-  default =  "alertmanager"
+variable "TAG_PREFIX" {
+  default = "docker.io/boxcutter/alertmanager"
 }
 
 variable "VERSION" {
   default = "0.27.0"
 }
 
-variable "CONTAINER_REGISTRY" {
-  default = "docker.io/boxcutter"
-}
-
 # There's no darwin-based Docker, so if we're running on macOS, change the platform to linux
 variable "LOCAL_PLATFORM" {
   default = regex_replace("${BAKE_LOCAL_PLATFORM}", "^(darwin)", "linux")
@@ -26,14 +22,15 @@ target "_common" {
     ALERTMANAGER_SHA256_ARMHF = "10800f0256873c2eed843297f2a49958f743f6497eada7f7fb8f35aa1d009b53"
   }
   tags = [
-    "${CONTAINER_REGISTRY}/${IMAGE_NAME}:${VERSION}",
-    "${CONTAINER_REGISTRY}/${IMAGE_NAME}:latest"
+    "${TAG_PREFIX}:${VERSION}",
+    "${TAG_PREFIX}:latest"
   ]
   labels = {
     "org.opencontainers.image.source" = "https://github.com/boxcutter/oci"
     "org.opencontainers.image.licenses" = "Apache-2.0"
     "org.opencontainers.image.description" = "Prometheus Alertmanager."
-    "org.opencontainers.image.title" = "${IMAGE_NAME}"
+    "org.opencontainers.image.title" = "${TAG_PREFIX}"
+    "org.opencontainers.image.created" = "${timestamp()}"
     "dev.boxcutter.image.readme-filepath" = "prometheus/alertmanager/README.md"
   }
 }