diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
index 0d6d7a02..c0dc4c16 100644
--- a/.devcontainer/Dockerfile
+++ b/.devcontainer/Dockerfile
@@ -1,3 +1,3 @@
 # Make sure RUBY_VERSION matches the Ruby version in .ruby-version
-ARG RUBY_VERSION=3.4.7
+ARG RUBY_VERSION=4.0.1@sha256:12a310c7b6a14bb0dd45a1032748ada9d2baacb60944189447a87e85318d5fc3
 FROM ghcr.io/rails/devcontainer/images/ruby:$RUBY_VERSION