diff --git a/shell.nix b/shell.nix
index a1ba79d..a56d466 100644
--- a/shell.nix
+++ b/shell.nix
@@ -3,6 +3,10 @@
 let
   my-python-packages = ps: with ps; [
     psutil
+
+    # Build dependencies only.
+    build
+    twine
   ];
   my-python = pkgs.python3.withPackages my-python-packages;
 in my-python.env