if the plugin is built with 1.431-SNAPSHOT core, we don't want that to automatically pick up ant & javadoc. We only want that for plugins built against 1.430 or earlier.

core/src/main/java/hudson/ClassicPluginStrategy.java

@@ -239,8 +239,8 @@ public class ClassicPluginStrategy implements PluginStrategy {
         new DetachedPlugin("maven-plugin","1.296","1.296"),
         new DetachedPlugin("subversion","1.310","1.0"),
         new DetachedPlugin("cvs","1.340","0.1"),
-        new DetachedPlugin("ant","1.431","1.0"),
-        new DetachedPlugin("javadoc","1.431","1.0")
+        new DetachedPlugin("ant","1.430.*","1.0"),
+        new DetachedPlugin("javadoc","1.430.*","1.0")
     );
 
     /**