diff --git a/Dockerfile b/Dockerfile
index 8c1a3d7..8104d24 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM docker.io/ubuntu:20.04
+FROM docker.io/amd64/ubuntu:20.04
 
 LABEL maintainer="Jake Jarvis <jake@jarv.is>"
 LABEL repository="https://github.com/jakejarvis/y2k"
diff --git a/build.sh b/build.sh
index 73adf9c..a9a9898 100755
--- a/build.sh
+++ b/build.sh
@@ -13,3 +13,7 @@ doctl registry login
 
 docker build -t registry.digitalocean.com/jakejarvis/y2k:latest --no-cache "$YOU_ARE_HERE"
 docker push registry.digitalocean.com/jakejarvis/y2k:latest
+
+# on DigitalOcean, old tags need to be purged manually:
+#   doctl registry garbage-collection start --force --include-untagged-manifests
+#   doctl registry garbage-collection get-active