diff --git a/core/src/main/java/hudson/tasks/Ant.java b/core/src/main/java/hudson/tasks/Ant.java
index 7c932f3c5ace9d9f3c5d7e8eedb32db4aea18104..1c3f96e6611c1965c6041a5e1acd76abfdc7dc05 100644
--- a/core/src/main/java/hudson/tasks/Ant.java
+++ b/core/src/main/java/hudson/tasks/Ant.java
@@ -229,7 +229,7 @@ public class Ant extends Builder {
 
     public static final DescriptorImpl DESCRIPTOR = new DescriptorImpl();
 
-    public static final class DescriptorImpl extends Descriptor<Builder> {
+    public static class DescriptorImpl extends Descriptor<Builder> {
         @CopyOnWrite
         private volatile AntInstallation[] installations = new AntInstallation[0];
 
@@ -238,6 +238,10 @@ public class Ant extends Builder {
             load();
         }
 
+        protected DescriptorImpl(Class<? extends Ant> clazz) {
+            super(clazz);
+        }
+
         protected void convert(Map<String,Object> oldPropertyBag) {
             if(oldPropertyBag.containsKey("installations"))
                 installations = (AntInstallation[]) oldPropertyBag.get("installations");