diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index d7e7d35..543cbd5 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -1,7 +1,7 @@
-image: "docker:latest"
+image: "docker:latest@sha256:7d85d0eda291f1a7ab6df4a9d1802b5ad4cf9145a088bd11188c78dcb5c7392b"
 
 services:
-  - "docker:dind"
+  - "docker:dind@sha256:7d85d0eda291f1a7ab6df4a9d1802b5ad4cf9145a088bd11188c78dcb5c7392b"
 
 before_script:
   - "docker login -u \"$CI_REGISTRY_USER\" -p \"$CI_REGISTRY_PASSWORD\" $CI_REGISTRY"
diff --git a/Dockerfile b/Dockerfile
index ac3167a..2aee6aa 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>"
 
 # hadolint ignore=DL3008,SC3009,SC2086