diff --git a/pkg/Dockerfile b/pkg/Dockerfile
index 6ad35ce..7587acf 100644
--- a/pkg/Dockerfile
+++ b/pkg/Dockerfile
@@ -1,4 +1,4 @@
-FROM docker.io/dunglas/frankenphp:1-php8.5-alpine
+FROM docker.io/dunglas/frankenphp:1-php8.5-alpine@sha256:7d92f9b2674d6a07a73e39ea771530e3bb2386a88c3b37b6eff00d3fbc02655e
 LABEL maintainer="Julien Cabillot <dockerimages@cabillot.eu>"
 
 WORKDIR "/app"