Array of BitArrays definition compiles in DMD but not in GDC.

[TheGag96 via Digitalmars-d-learn]

In my code I'm passing an array of BitArrays to a constructor 
like this (though mostly as a placeholder):

  Terrain t = new Terrain(1, 15, [
    BitArray([1, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1]),
    BitArray([1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1]),
    BitArray([0, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1]),
    BitArray([0, 0, 1, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1]),
    BitArray([0, 0, 0, 1, 1, 0, 1, 1, 1, 1, 1, 1, 1]),
    BitArray([1, 1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1]),
  ]);
The code compiles fine when using DMD 2.068.1 but GDC 5.2.1, I 
get this error for every line:

error: cannot implicityly convert expression ([stuff]) of type 
int[] to ulong

Why does this compiler difference exist and how do I get around 
it? Thanks!