diff --git a/Dockerfile b/Dockerfile
index 5a70e69..277ba36 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,5 +1,5 @@
 # Stage 1: Download and extract ocm binary
-FROM alpine AS downloader
+FROM alpine@sha256:4bcff63911fcb4448bd4fdacec207030997caf25e9bea4045fa6c8c44de311d1 AS downloader
 ARG TARGETOS
 ARG TARGETARCH
 RUN apk add --no-cache curl tar