diff --git a/2019/d07/ex1/ex1.py b/2019/d07/ex1/ex1.py
index 1808ec8..5bea100 100755
--- a/2019/d07/ex1/ex1.py
+++ b/2019/d07/ex1/ex1.py
@@ -1,5 +1,9 @@
 #!/usr/bin/env python
 
+# Mypy has issues with assigning Callable to fields of objects
+# See https://github.com/python/mypy/issues/708
+# type: ignore
+
 import itertools
 import sys
 from copy import deepcopy
diff --git a/flake.nix b/flake.nix
index 614040f..ba32138 100644
--- a/flake.nix
+++ b/flake.nix
@@ -56,6 +56,9 @@
 
         devShell = pkgs.mkShell {
           buildInputs = with pkgs; [
+            pkgs.python3Packages.black
+            pkgs.python3Packages.isort
+            pkgs.python3Packages.mypy
             python3
           ];