diff --git a/.github/workflows/CI.yml b/.github/workflows/CI.yml
index f277de15..034cd954 100644
--- a/.github/workflows/CI.yml
+++ b/.github/workflows/CI.yml
@@ -12,7 +12,7 @@ jobs:
       # don't cancel remaining matrix steps on failure
       fail-fast: false
       matrix:
-        java: [11, 17]
+        java: [11, 17, 21]
 
     steps:
       - uses: actions/checkout@v2