     # Starts a server responsible for keeping track which files
     # were compiled and the dependencies between them.
     {:ok, pid} = Agent.start_link(fn -> {entries, sources} end)
+    long_compilation_threshold = opts[:long_compilation_threshold] || 5
 
     try do
-      long_compilation_threshold = Keyword.get(opts, :long_compilation_threshold, 5)
-      _ = Kernel.ParallelCompiler.files :lists.usort(stale),
+      _ = Kernel.ParallelCompiler.files stale,
             [each_module: &each_module(pid, dest, cwd, &1, &2, &3),
              each_long_compilation: &each_long_compilation(&1, long_compilation_threshold),
              long_compilation_threshold: long_compilation_threshold,


  defp compile_manifest(manifest, entries, sources, stale, dest, opts) do
    Mix.Utils.compiling_n(length(stale), :ex)
    Mix.Project.ensure_structure()
    true = Code.prepend_path(dest)

    set_compiler_opts(opts)
    cwd = File.cwd!


  end

  defp set_compiler_opts(opts) do
    opts
    |> Keyword.take(Code.available_compiler_options)
    |> Code.compiler_options()
  end

  defp each_module(pid, dest, cwd, source, module, binary) do
