diff --git a/.github/workflows/gradle.yml b/.github/workflows/gradle.yml
index f132b42..0f5c621 100644
--- a/.github/workflows/gradle.yml
+++ b/.github/workflows/gradle.yml
@@ -18,7 +18,7 @@ jobs:
     strategy:
       fail-fast: false # ensures build runs for all three JDKs
       matrix:
-        java: [ '8', '11', '17' ]
+        java: [ '8', '11', '17', '21' ]
 
     name: Java ${{ matrix.Java }}