diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 7af63409..7834987f 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -14,7 +14,7 @@ jobs:
       fail-fast: false
       matrix:
         group: [ cfi-tests, downstream-ontology, downstream-security-demo, downstream-universe ]
-        jdk: [ 8, 11, 17 ]
+        jdk: [ 8, 11, 17, 21]
     runs-on: ubuntu-latest
     steps:
       - name: Install dependencies
@@ -52,7 +52,7 @@ jobs:
           python3 -m pip install --upgrade pip
           if [ -f requirements.txt ]; then pip install -r requirements.txt; fi
       - name: Spotless Check
-        if: matrix.jdk == 11 || matrix.jdk == 17
+        if: matrix.jdk != 8
         run: ./gradlew spotlessCheck
       - name: Build
         run: |