diff --git a/.ruby-version b/.ruby-version
index 86fb65044..fcdb2e109 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.3.7
+4.0.0
diff --git a/Dockerfile b/Dockerfile
index c24012d84..1710215a8 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,4 +1,4 @@
-FROM ruby:3.3.7-slim@sha256:696f37b3cd55288b5127850e3eeae67dd20595ab77a6724f7bb05baa8c6b4878
+FROM ruby:4.0.0-slim@sha256:6a08f2a66d5bff1204add452ebdf2f3819ed1212c6269d0bc152e14f375aca3e
 
 # Define args that can be supplied with
 # `docker build --build-args RAILS_ENV=<env>`, defaults to production.