How to properly match varargs in Mockito

I've been trying to get to mock a method with vararg parameters using Mockito:

interface A {
  B b(int x, int y, C... c);
}

A a = mock(A.class);
B b = mock(B.class);

when(a.b(anyInt(), anyInt(), any(C[].class))).thenReturn(b);
assertEquals(b, a.b(1, 2));

This doesn't work, however if I do this instead:

when(a.b(anyInt(), anyInt())).thenReturn(b);
assertEquals(b, a.b(1, 2));

This works, despite that I have completely omitted the varargs argument when stubbing the method.

Any clues?