diff --git a/Dockerfile b/Dockerfile
index 8c766e7..ba8c100 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:ddfff516ea52b4336019888b3ac492f6036c1c840b1b18a2629f6b80f8fc5fc6
 
 RUN apt-get update \
   && apt-get install -y --no-install-recommends aptly createrepo-c gnupg ca-certificates dpkg-dev \