diff --git a/Dockerfile b/Dockerfile
index 0ca2248..525cc5b 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine@sha256:865b95f46d98cf867a156fe4a135ad3fe50d2056aa3f25ed31662dff6da4eb62
 
 # ca-certificates is needed to download files from S3
 RUN apk update && apk add ca-certificates && rm -rf /var/cache/apk/*