diff --git a/pkgs/development/python-modules/logical-unification/default.nix b/pkgs/development/python-modules/logical-unification/default.nix
index b89fcb25339..0762d3986cc 100644
--- a/pkgs/development/python-modules/logical-unification/default.nix
+++ b/pkgs/development/python-modules/logical-unification/default.nix
@@ -3,6 +3,7 @@
 , fetchFromGitHub
 , toolz
 , multipledispatch
+, py
 , pytestCheckHook
 , pytest-html
 , pytest-benchmark
@@ -25,6 +26,7 @@ buildPythonPackage rec {
   ];
 
   checkInputs = [
+    py
     pytestCheckHook
     pytest-html
     pytest-benchmark  # Needed for the `--benchmark-skip` flag