Axlsx ignores image.start_at

Just a small problem that i'm facing with axlsx_rails images.
currently i have this:

sheet.add_image(:image_src => img, :noSelect => false, :noMove => false) do |image|
      image.start_at 5, 5
      image.end_at 15, 20 
  end

and it seems to somehow ignore the image.start_at line. No matter what values i give it, the image starts from 0,0 (Cell A1) and stretches until the values specified in image.end_at.
Does anyone know what could be causing this or how to get around it ? I need to simply put the image inside 3 merged cells.