diff --git a/pkgs/development/python-modules/pyhanko-certvalidator/default.nix b/pkgs/development/python-modules/pyhanko-certvalidator/default.nix
index 5018f8f924a5..5e83dc793ca5 100644
--- a/pkgs/development/python-modules/pyhanko-certvalidator/default.nix
+++ b/pkgs/development/python-modules/pyhanko-certvalidator/default.nix
@@ -5,7 +5,6 @@
 , cryptography
 , fetchFromGitHub
 , freezegun
-, openssl
 , oscrypto
 , pytest-asyncio
 , pytestCheckHook
@@ -29,6 +28,11 @@ buildPythonPackage rec {
     hash = "sha256-q2YxncyMHmbRmcoLb68huK02CYiKqF2CFRl8vkUfxg4=";
   };
 
+  postPatch = ''
+    substituteInPlace pyproject.toml \
+      --replace ', "pytest-runner",' ""
+  '';
+
   nativeBuildInputs = [
     setuptools
   ];