diff --git a/spock-core/src/main/java/org/spockframework/buildsupport/EmptyAnnotationVisitor.java b/spock-core/src/main/java/org/spockframework/buildsupport/EmptyAnnotationVisitor.java
index d156d6bf53..e1e9357001 100644
--- a/spock-core/src/main/java/org/spockframework/buildsupport/EmptyAnnotationVisitor.java
+++ b/spock-core/src/main/java/org/spockframework/buildsupport/EmptyAnnotationVisitor.java
@@ -18,7 +18,7 @@
 
 class EmptyAnnotationVisitor extends AnnotationVisitor {
   public EmptyAnnotationVisitor() {
-    super(Opcodes.ASM4);
+    super(Opcodes.ASM9);
   }
 
   @Override
diff --git a/spock-core/src/main/java/org/spockframework/buildsupport/SpecClassFileVisitor.java b/spock-core/src/main/java/org/spockframework/buildsupport/SpecClassFileVisitor.java
index 4a10a34a49..55b2736bcb 100644
--- a/spock-core/src/main/java/org/spockframework/buildsupport/SpecClassFileVisitor.java
+++ b/spock-core/src/main/java/org/spockframework/buildsupport/SpecClassFileVisitor.java
@@ -25,7 +25,7 @@ class SpecClassFileVisitor extends ClassVisitor {
   private boolean isAbstract;
 
   SpecClassFileVisitor() {
-    super(Opcodes.ASM4);
+    super(Opcodes.ASM9);
   }
 
   public boolean isSpec() {
@@ -73,4 +73,3 @@ public MethodVisitor visitMethod(int i, String s, String s1, String s2, String[]
   @Override
   public void visitEnd() {}
 }
-