Higher page margin seems to break algorithm

[jtreitz]

Prawn::Document.new(margin: 70) do
  5.times do
    group do |g|
      12.times { |i| g.text "Paragraphs not separated unless necessary (#{i})" }
    end
  end
  render_file 'test.pdf'
end

Expected outcome: 12 paragraphs are kept together Actual outcome: Paragraphs are split

test.pdf