AntBuilder can't run a pure JUnit4 task, whereas Ant can do

If you have a pure JUnit4 test suite with @RunWith(Suite.class) and @Suite.SuiteClasses(

) and try to execute this via AntBuilder() no tests can be executed because it states 'No tests found in ...'
An equivalent Ant 1.9.4 <junit> task with the same compiled test suite finds the tests.
I didn't had the issue with Groovy 2.1.7. But it seems this version added a suite() method with a JUnit4TestAdapter.
If you add

public static Test suite() { return JUnit4TestAdapter(<testclass>)}

to your test suite everything works fine even in Groovy 2.4.3.