assertEquals() raises IllegalAccessError for Lists

The following test causes an exception ...

void testIt() {
assertEquals([1,2], [3,4])
}

That should fail yes, bit raises the following exception ...

java.lang.IllegalAccessError: tried to access method junit.framework.Assert.failNotEquals(Ljava/lang/String;Ljava/lang/Object;Ljava/lang/Object;)V from class groovy.util.GroovyTestCase
at groovy.util.GroovyTestCase.assertEquals(GroovyTestCase.java:385)
at groovy.util.GroovyTestCase.assertEquals(GroovyTestCase.java:389)