diff --git a/.devcontainer/Dockerfile b/.devcontainer/Dockerfile
index 0d6d7a02..53626df1 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=3.4.7@sha256:5ca3f3c0be2e78f1920b1b0f40c82aaafd4ed2ca0201b622ebc661b1bfce3c4e
 FROM ghcr.io/rails/devcontainer/images/ruby:$RUBY_VERSION