diff --git a/Dockerfile b/Dockerfile
index fc0a5a7..5dd0c82 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,9 +1,8 @@
 # https://github.com/containers/podman/blob/main/contrib/podmanimage/stable/Containerfile
 # https://hub.docker.com/r/jenkins/inbound-agent/tags
 
-ARG BASE="alpine-jdk17"
 
-FROM jenkins/inbound-agent:${BASE}
+FROM jenkins/inbound-agent:alpine-jdk17@sha256:9ffaf2ae447d87b274be28958432070a7b980eca99287bb8bb4f58125364071b
 
 ARG BUILDUSER=jenkins