diff --git a/pkgs/development/python-modules/hypothesmith/default.nix b/pkgs/development/python-modules/hypothesmith/default.nix
index d1a6625e8c7b..8fe65b3f4d7b 100644
--- a/pkgs/development/python-modules/hypothesmith/default.nix
+++ b/pkgs/development/python-modules/hypothesmith/default.nix
@@ -18,6 +18,10 @@ buildPythonPackage rec {
 
   checkInputs = [ black parso pytestCheckHook pytest-cov pytest-xdist ];
 
+  pytestFlagsArray = [
+    "--numprocesses $NIX_BUILD_CORES"
+  ];
+
   pythonImportsCheck = [ "hypothesmith" ];
 
   meta = with lib; {