diff --git a/base/Dockerfile b/base/Dockerfile
index feedefa..8e072bc 100644
--- a/base/Dockerfile
+++ b/base/Dockerfile
@@ -1,3 +1,3 @@
-FROM ubuntu:devel
+FROM ubuntu:devel@sha256:9a7b522028ebc43104df4b9d9e3e8b002f4dbe316d6f09464a58306baeed0423
 RUN echo '{:version 18}' > dog.json
 CMD ["cat", "dog.json"]