diff --git a/.circleci/config.yml b/.circleci/config.yml
index 2f8bfe5..ad1dc0f 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -6,7 +6,7 @@ jobs:
     parallelism: 1
     working_directory: ~/socrates
     docker:
-      - image: cimg/ruby:3.0.3
+      - image: cimg/ruby:4.0.0
     steps:
       - checkout
       - ruby/install-deps
diff --git a/.ruby-version b/.ruby-version
index 75a22a2..fcdb2e1 100644
--- a/.ruby-version
+++ b/.ruby-version
@@ -1 +1 @@
-3.0.3
+4.0.0