diff --git a/Dockerfile b/Dockerfile
index 8c766e7..4ec2ed0 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM gcr.io/google.com/cloudsdktool/google-cloud-cli:slim
+FROM gcr.io/google.com/cloudsdktool/google-cloud-cli:slim@sha256:55e3623f85589335f7f41725a71b31e9c1e49be71009610ae1cc205acda5f10f
 
 RUN apt-get update \
   && apt-get install -y --no-install-recommends aptly createrepo-c gnupg ca-certificates dpkg-dev \