diff --git a/Dockerfile b/Dockerfile
index 9f59af4..4550d37 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ubuntu:18.04
+FROM ubuntu:18.04@sha256:152dc042452c496007f07ca9127571cb9c29697f42acbfad72324b2bb2e43c98
 LABEL maintainer="Julien Cabillot <dockerimages@cabillot.eu>"
 
 ENV DEBIAN_FRONTEND=noninteractive