diff --git a/pkgs/development/python-modules/convertertools/default.nix b/pkgs/development/python-modules/convertertools/default.nix
index 5d51a59946a6..2114a6955ed2 100644
--- a/pkgs/development/python-modules/convertertools/default.nix
+++ b/pkgs/development/python-modules/convertertools/default.nix
@@ -11,6 +11,7 @@
 
   # checks
   pytestCheckHook,
+  pytest-cov-stub,
 }:
 
 buildPythonPackage rec {
@@ -27,17 +28,16 @@ buildPythonPackage rec {
     hash = "sha256-Oy1Nf/mS2Lr2N7OB27QDlW+uuhafib2kolEXzXLppWU=";
   };
 
-  postPatch = ''
-    sed -i "/--cov/d" pyproject.toml
-  '';
-
   build-system = [
     cython
     poetry-core
     setuptools
   ];
 
-  nativeCheckInputs = [ pytestCheckHook ];
+  nativeCheckInputs = [
+    pytestCheckHook
+    pytest-cov-stub
+  ];
 
   pythonImportsCheck = [ "convertertools" ];