diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index d562d6e..f702d96 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -23,7 +23,7 @@ jobs:
       matrix: # match with maven-enforcer-plugin rules in pom.xml
         include:
           - name: build-arg
-            version: 21.0.2_p13
+            version: 21.0.3_p9
           - name: implicit
             version: master
     steps:
diff --git a/Dockerfile b/Dockerfile
index 3f62155..83b9ea7 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -6,7 +6,7 @@
 # docker_parent_image is the base layer of full and jre image
 #
 # Use latest version here: https://github.com/orgs/openzipkin/packages/container/package/alpine
-ARG docker_parent_image=ghcr.io/openzipkin/alpine:3.19.1
+ARG docker_parent_image=ghcr.io/openzipkin/alpine:3.20.0
 
 # java_version and java_home are hard-coded here to allow the following:
 #  * `docker build https://github.com/openzipkin/docker-java.git`
@@ -17,7 +17,7 @@ ARG docker_parent_image=ghcr.io/openzipkin/alpine:3.19.1
 # When updating, also update the README
 #  * Use current version from https://pkgs.alpinelinux.org/packages?name=openjdk21, stripping
 #    the `-rX` at the end.
-ARG java_version=21.0.2_p13
+ARG java_version=21.0.3_p9
 ARG java_home=/usr/lib/jvm/java-21-openjdk
 
 # We copy files from the context into a scratch container first to avoid a problem where docker and
diff --git a/README.md b/README.md
index 927534f..b940346 100644
--- a/README.md
+++ b/README.md
@@ -15,10 +15,10 @@ This is an internal base layer primarily used in [zipkin](https://github.com/ope
 
 To try the image, run the `java -version` command:
 ```bash
-$ docker run --rm ghcr.io/openzipkin/java:21.0.2_p13 -version
-openjdk version "21.0.2" 2024-01-16
-OpenJDK Runtime Environment (build 21.0.2+13-alpine-r2)
-OpenJDK 64-Bit Server VM (build 21.0.2+13-alpine-r2, mixed mode, sharing)
+$ docker run --rm ghcr.io/openzipkin/java:21.0.3_p9 -version
+openjdk version "21.0.3" 2024-04-16
+OpenJDK Runtime Environment (build 21.0.3+9-alpine-r0)
+OpenJDK 64-Bit Server VM (build 21.0.3+9-alpine-r0, mixed mode, sharing)
 ```
 
 ## Release process
@@ -39,19 +39,19 @@ Build the [Dockerfile](Dockerfile) using the current version without the
 revision classifier from here:
  * https://pkgs.alpinelinux.org/packages?name=openjdk21
 ```bash
-# Note 21.0.2_p13 not 21.0.2_p13-r2!
-./build-bin/build 21.0.2_p13
+# Note 21.0.3_p9 not 21.0.3_p9-r2!
+./build-bin/build 21.0.3_p9
 ```
 
 Next, verify the built image matches that version:
 ```bash
 $ docker run --rm openzipkin/java:test -version
-openjdk version "21.0.2" 2024-01-16
-OpenJDK Runtime Environment (build 21.0.2+13-alpine-r2)
-OpenJDK 64-Bit Server VM (build 21.0.2+13-alpine-r2, mixed mode, sharing)
+openjdk version "21.0.3" 2024-04-16
+OpenJDK Runtime Environment (build 21.0.3+9-alpine-r0)
+OpenJDK 64-Bit Server VM (build 21.0.3+9-alpine-r0, mixed mode, sharing)
 ```
 
-To release the image, push a tag matching the arg to `build-bin/build` (ex `21.0.2_p13`).
+To release the image, push a tag matching the arg to `build-bin/build` (ex `21.0.3_p9`).
 This triggers a [GitHub Actions](https://github.com/openzipkin/docker-java/actions) job to push the image.
 
 ## java.lang.ClassNotFoundException