diff --git a/lib/2015/day_02.ex b/lib/2015/day_02.ex
index 10cd868..dd14f34 100644
--- a/lib/2015/day_02.ex
+++ b/lib/2015/day_02.ex
@@ -35,12 +35,12 @@ defmodule AdventOfCode.Y2015.Day02 do
     |> Enum.reduce(&Kernel.+/2)
   end
 
-  @spec required_paper([non_neg_integer(), ...]) :: non_neg_integer()
+  @spec required_paper([pos_integer(), ...]) :: pos_integer()
   defp required_paper(sides) do
     surface_area(sides) + minimum(area_per_dim(sides))
   end
 
-  @spec surface_area([non_neg_integer(), ...]) :: non_neg_integer()
+  @spec surface_area([pos_integer(), ...]) :: pos_integer()
   defp surface_area(sides) do
     sides
     |> area_per_dim()
@@ -48,17 +48,17 @@ defmodule AdventOfCode.Y2015.Day02 do
     |> Kernel.*(2)
   end
 
-  @spec area_per_dim([non_neg_integer(), ...]) :: [non_neg_integer(), ...]
+  @spec area_per_dim([pos_integer(), ...]) :: [pos_integer(), ...]
   defp area_per_dim([width, length, height]) do
     [length * width, width * height, height * length]
   end
 
-  @spec minimum([non_neg_integer(), ...]) :: non_neg_integer()
+  @spec minimum([pos_integer(), ...]) :: pos_integer()
   defp minimum([side_1, side_2, side_3]) do
     side_1 |> min(side_2) |> min(side_3)
   end
 
-  @spec smallest_perimeter_plus_volume([non_neg_integer(), ...]) :: non_neg_integer()
+  @spec smallest_perimeter_plus_volume([pos_integer(), ...]) :: pos_integer()
   defp smallest_perimeter_plus_volume([width, length, height]) do
     [width + length, length + height, height + width]
     |> Enum.min()
diff --git a/lib/advent_of_code.ex b/lib/advent_of_code.ex
index 801659b..26954ec 100644
--- a/lib/advent_of_code.ex
+++ b/lib/advent_of_code.ex
@@ -6,7 +6,7 @@ defmodule AdventOfCode do
   @latest_year 2023
 
   @type year() :: 2015 | 2016 | 2017 | 2018 | 2019 | 2020 | 2021 | 2022 | 2023
-  @type day() :: non_neg_integer()
+  @type day() :: pos_integer()
 
   @doc """
   Returns the latest year solved.
diff --git a/lib/helpers/input_reader.ex b/lib/helpers/input_reader.ex
index 180be6e..e197938 100644
--- a/lib/helpers/input_reader.ex
+++ b/lib/helpers/input_reader.ex
@@ -10,7 +10,7 @@ defmodule AdventOfCode.Helpers.InputReader do
   is configurable because some AoC problems (i.e. Year 2017 day 19) has significant leading
   or trailing space(s)
   """
-  @spec read_from_file(non_neg_integer(), non_neg_integer(), boolean()) :: binary()
+  @spec read_from_file(pos_integer(), pos_integer(), boolean()) :: binary()
   def read_from_file(year, day, trim \\ true) do
     case {trim, File.read!("#{@input_dir}/#{year}_#{day}.txt")} do
       {true, data} -> String.trim(data)