diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index bfa2c05..bb82b15 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,10 +24,10 @@ jobs:
 
       # Configuring caching is also recommended.
       # See https://github.com/actions/setup-java
-      - name: Setup Java 11
-        uses: actions/setup-java@v3
+      - name: Setup Java
+        uses: actions/setup-java@v4
         with:
-          java-version: '11'
+          java-version: '21'
           distribution: 'corretto'
           cache: 'sbt'
 
diff --git a/cloudformation/cfn.yaml b/cloudformation/cfn.yaml
index 3c11348..04bdecf 100644
--- a/cloudformation/cfn.yaml
+++ b/cloudformation/cfn.yaml
@@ -61,7 +61,7 @@ Resources:
               - s3:GetObject
             Resource: !Sub arn:aws:s3:::${ConfigBucket}/*
       Handler: com.gu.anghammarad.Lambda::handleRequest
-      Runtime: java11
+      Runtime: java21
       MemorySize: 512
       Timeout: 30
       CodeUri: