flatten() does not work on byte[]

The following test script highlights the problem:

def test =(byte)0
assert (test.class == java.lang.Byte)

def test2 = [] << test
assert (test2[0].class == java.lang.Byte)

test2 << ('test'.bytes)
assert (test2[1][0].class == java.lang.Byte)

test2.flatten()

// This fails. The value returned by current code is 2
assert (test2.size() == 5)