diff --git a/k8s/challenge53/Dockerfile b/k8s/challenge53/Dockerfile
index c6098907b..0086e568b 100644
--- a/k8s/challenge53/Dockerfile
+++ b/k8s/challenge53/Dockerfile
@@ -1,4 +1,4 @@
-FROM ubuntu:25.04
+FROM ubuntu:plucky-20241213
 RUN useradd -m -u 2000 wrongsecrets
 
 COPY --chown=wrongsecrets executables/ /home/wrongsecrets/
diff --git a/k8s/challenge53/Dockerfile.debug b/k8s/challenge53/Dockerfile.debug
index 4e1ff7719..20b825aac 100644
--- a/k8s/challenge53/Dockerfile.debug
+++ b/k8s/challenge53/Dockerfile.debug
@@ -1,4 +1,4 @@
-FROM ubuntu:25.04
+FROM ubuntu:plucky-20241213
 
 RUN useradd -m -u 2000 wrongsecrets