diff --git a/Dockerfile b/Dockerfile
index b847670..d2f7be2 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine:3.20.1 AS builder
+FROM alpine:3.20.1@sha256:b89d9c93e9ed3597455c90a0b88a8bbb5cb7188438f70953fede212a0c4394e0 AS builder
 
 ARG LIGHTTPD_TARBALL="https://download.lighttpd.net/lighttpd/releases-1.4.x/lighttpd-1.4.76.tar.gz"
 ARG LIGHTTPD_SHA256="ba14a030889518194fd88b33e419d51cc38c8fe917126d5a7a965be79b53e995"