diff --git a/qsprpred/extra/data/descriptors/sets.py b/qsprpred/extra/data/descriptors/sets.py
index d66102b1..68a1df67 100644
--- a/qsprpred/extra/data/descriptors/sets.py
+++ b/qsprpred/extra/data/descriptors/sets.py
@@ -132,6 +132,7 @@ def __init__(self, descs: list[str] | None = None):
         super().__init__()
         self._descs = descs
         self._mold2 = Mold2_calculator()
+        assert os.path.exists(self._mold2._zipfile), "Mold2 binary not found"
         self._defaultDescs = self._mold2.calculate(
             [Chem.MolFromSmiles("C")], show_banner=False
         ).columns.tolist()
diff --git a/qsprpred/extra/data/descriptors/tests.py b/qsprpred/extra/data/descriptors/tests.py
index d5c8c445..89fbb919 100644
--- a/qsprpred/extra/data/descriptors/tests.py
+++ b/qsprpred/extra/data/descriptors/tests.py
@@ -58,6 +58,7 @@ def setUp(self):
     @skipIf(platform.system() == "Darwin", "Mold2 not supported on Mac OS")
     def testMold2(self):
         """Test the Mold2 descriptor calculator."""
+        self.dataset.nJobs = 1
         self.dataset.addDescriptors([Mold2()])
         self.assertEqual(self.dataset.X.shape, (len(self.dataset), 777))
         self.assertTrue(self.dataset.X.any().any())