fluent-ffmpeg: how to merge many files with across fade between them

Question

Well, first of all, a i have some audio inputs and i want to merge all into a single audio file with acrossfade between them.

file1.mp3, file2.mp3...fileN.mp3

I'm doing a reduce to include all the inputs, like this:

inputs.reduce((result, file) => result.addInput(file), ffmpeg())

And for adding the acrossfade, i created a function that receives my inputs and build the complexFilter. The returned filters looks like this:

[
  {
    filter: 'acrossfade',
    inputs: [ '0', '1' ],
    options: { d: 5, overlap: '1', c1: 'nofade', c2: 'nofade' },
    outputs: 'a0'
  },
  {
    filter: 'acrossfade',
    inputs: [ 'a0', '2' ],
    options: { d: 5, overlap: '1', c1: 'nofade', c2: 'nofade' },
    outputs: 'a1'
  },
  {
    filter: 'acrossfade',
    inputs: [ 'a1', '3' ],
    options: { d: 5, overlap: '1', c1: 'nofade', c2: 'nofade' },
    outputs: 'a2'
  }
]

After generating my filter, i'm applying it to my previous command with complexFilter:

const filter = buildBlockFilter(inputs);

inputs
   .reduce((result, { file }) => result.addInput(file), ffmpeg())
   .complexFilter(filter)
   .mergeToFile(output)
   .on('error', (error) => console.log(error));

After running it, the files are being merged correctly, but without any fade between them, any tips about how to fix this?