diff --git a/flask/app/Dockerfile b/flask/app/Dockerfile
index d0be3b5..3c6491d 100644
--- a/flask/app/Dockerfile
+++ b/flask/app/Dockerfile
@@ -1,5 +1,5 @@
 # syntax=docker/dockerfile:1.4
-FROM --platform=$BUILDPLATFORM python:3.10-alpine AS builder
+FROM --platform=$BUILDPLATFORM python:3.10-alpine@sha256:c9d3c11e89887c82efeb4f4fee8771a406cf42f41aebbd23148906d5fe3c1426 AS builder
 
 WORKDIR /app