diff --git a/hpi/flake.nix b/hpi/flake.nix
index 19c2769..2c3ef6f 100644
--- a/hpi/flake.nix
+++ b/hpi/flake.nix
@@ -42,6 +42,7 @@
           setuptools-scm
           pytest
           geopy
+          mypy
         ]);
       in
       {