diff --git a/Dockerfile b/Dockerfile
index 0ca2248..a24df2f 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM alpine
+FROM alpine@sha256:b97e2a89d0b9e4011bb88c02ddf01c544b8c781acf1f4d559e7c8f12f1047ac3
 
 # ca-certificates is needed to download files from S3
 RUN apk update && apk add ca-certificates && rm -rf /var/cache/apk/*