diff --git a/pkgs/development/python-modules/pypytools/default.nix b/pkgs/development/python-modules/pypytools/default.nix
index e88891172de..1828ede0a92 100644
--- a/pkgs/development/python-modules/pypytools/default.nix
+++ b/pkgs/development/python-modules/pypytools/default.nix
@@ -28,6 +28,7 @@ buildPythonPackage rec {
   checkInputs = [
     freezegun
     numpy
+    py
     pytestCheckHook
   ];