diff --git a/.github/workflows/gradleBuild.yml b/.github/workflows/gradleBuild.yml
index a55188b..485d287 100644
--- a/.github/workflows/gradleBuild.yml
+++ b/.github/workflows/gradleBuild.yml
@@ -31,6 +31,7 @@ jobs:
           - '18'
           - '19'
           - '20'
+          - '21'
         distribution:
           - 'zulu'
 
diff --git a/build.gradle b/build.gradle
index 2f25def..35af0d1 100644
--- a/build.gradle
+++ b/build.gradle
@@ -199,6 +199,11 @@ allprojects {
 
             all {
                 resolutionStrategy.eachDependency { DependencyResolveDetails details ->
+                    if (details.requested.group == 'org.ow2.asm' &&
+                        details.requested.name == 'asm') {
+                        details.useVersion '9.5'
+                        details.because 'workaround for spotbugs not yet supporting JDK 21 class formats'
+                    }
 /*
                     if (details.requested.group == 'com.fasterxml.jackson' &&
                         details.requested.name == 'jackson-bom' &&