diff --git a/molpipeline/explainability/visualization/visualization.py b/molpipeline/explainability/visualization/visualization.py
index a5d436bf..b4bd4f15 100644
--- a/molpipeline/explainability/visualization/visualization.py
+++ b/molpipeline/explainability/visualization/visualization.py
@@ -67,7 +67,7 @@ def _make_grid_from_mol(
     mol_height = yl[1] - yl[0]
     mol_width = xl[1] - xl[0]
 
-    height_to_width_ratio_mol = mol_height / mol_width
+    height_to_width_ratio_mol = mol_height / (1e-16 + mol_width)
     # the grids height / weight is the canvas height / width
     height_to_width_ratio_canvas = grid_resolution[1] / grid_resolution[0]
 
diff --git a/tests/test_explainability/test_visualization/test_visualization.py b/tests/test_explainability/test_visualization/test_visualization.py
index 880e8aa0..3a001f5a 100644
--- a/tests/test_explainability/test_visualization/test_visualization.py
+++ b/tests/test_explainability/test_visualization/test_visualization.py
@@ -27,13 +27,13 @@
 _RANDOM_STATE = 67056
 
 
-def _get_test_shap_explanations() -> list[SHAPExplanation]:
-    """Get test explanations.
+def _get_test_morgan_rf_pipeline() -> Pipeline:
+    """Get a test pipeline with Morgan fingerprints and a random forest classifier.
 
     Returns
     -------
-    list[SHAPExplanation]
-        List of SHAP explanations.
+    Pipeline
+        Pipeline with Morgan fingerprints and a random forest classifier.
     """
     pipeline = Pipeline(
         [
@@ -45,26 +45,27 @@ def _get_test_shap_explanations() -> list[SHAPExplanation]:
             ),
         ]
     )
-    pipeline.fit(TEST_SMILES, CONTAINS_OX)
-
-    explainer = SHAPTreeExplainer(pipeline)
-    explanations = explainer.explain(TEST_SMILES)
-    return explanations
+    return pipeline
 
 
 class TestExplainabilityVisualization(unittest.TestCase):
     """Test the public interface of the visualization methods for explanations."""
 
-    explanations: ClassVar[list[SHAPExplanation]]
+    test_pipeline: ClassVar[Pipeline]
+    test_explainer: ClassVar[SHAPTreeExplainer]
+    test_explanations: ClassVar[list[SHAPExplanation]]
 
     @classmethod
     def setUpClass(cls) -> None:
         """Set up the tests."""
-        cls.explanations = _get_test_shap_explanations()
+        cls.test_pipeline = _get_test_morgan_rf_pipeline()
+        cls.test_pipeline.fit(TEST_SMILES, CONTAINS_OX)
+        cls.test_explainer = SHAPTreeExplainer(cls.test_pipeline)
+        cls.test_explanations = cls.test_explainer.explain(TEST_SMILES)
 
     def test_structure_heatmap_fingerprint_based_atom_coloring(self) -> None:
         """Test structure heatmap fingerprint-based atom coloring."""
-        for explanation in self.explanations:
+        for explanation in self.test_explanations:
             self.assertTrue(explanation.is_valid())
             self.assertIsInstance(explanation.atom_weights, np.ndarray)
             image = structure_heatmap(
@@ -78,7 +79,7 @@ def test_structure_heatmap_fingerprint_based_atom_coloring(self) -> None:
 
     def test_structure_heatmap_shap_explanation(self) -> None:
         """Test structure heatmap SHAP explanation."""
-        for explanation in self.explanations:
+        for explanation in self.test_explanations:
             self.assertTrue(explanation.is_valid())
             self.assertIsInstance(explanation.atom_weights, np.ndarray)
             image = structure_heatmap_shap(
@@ -89,20 +90,58 @@ def test_structure_heatmap_shap_explanation(self) -> None:
             self.assertIsNotNone(image)
             self.assertEqual(image.format, "PNG")
 
+    def test_explicit_hydrogens(self):
+        """Test that the visualization methods work with explicit hydrogens."""
+        mol_implicit_Hs = Chem.MolFromSmiles("C")
+        explanations1 = self.test_explainer.explain([Chem.MolToSmiles(mol_implicit_Hs)])
+        mol_added_Hs = Chem.AddHs(mol_implicit_Hs)
+        explanations2 = self.test_explainer.explain([Chem.MolToSmiles(mol_added_Hs)])
+        mol_explicit_Hs = Chem.MolFromSmiles("[H]C([H])([H])[H]")
+        explanations3 = self.test_explainer.explain([Chem.MolToSmiles(mol_explicit_Hs)])
+
+        # test explanations' atom weights
+        self.assertEqual(len(explanations1), 1)
+        self.assertEqual(len(explanations2), 1)
+        self.assertEqual(len(explanations3), 1)
+        self.assertIsNotNone(explanations1[0].atom_weights)
+        self.assertIsNotNone(explanations2[0].atom_weights)
+        self.assertIsNotNone(explanations3[0].atom_weights)
+        self.assertEqual(len(explanations1[0].atom_weights), 1)
+        self.assertEqual(len(explanations2[0].atom_weights), 1)
+        self.assertEqual(len(explanations3[0].atom_weights), 1)
+
+        # test visualization
+        all_explanations = explanations1 + explanations2 + explanations3
+        for explanation in all_explanations:
+            self.assertTrue(explanation.is_valid())
+            image = structure_heatmap(
+                explanation.molecule,
+                explanation.atom_weights,  # type: ignore[arg-type]
+                width=128,
+                height=128,
+            )  # type: ignore[union-attr]
+            self.assertIsNotNone(image)
+            self.assertEqual(image.format, "PNG")
+
 
 class TestSumOfGaussiansGrid(unittest.TestCase):
     """Test visualization methods for explanations."""
 
-    explanations: ClassVar[list[SHAPExplanation]]
+    test_pipeline: ClassVar[Pipeline]
+    test_explainer: ClassVar[SHAPTreeExplainer]
+    test_explanations: ClassVar[list[SHAPExplanation]]
 
     @classmethod
     def setUpClass(cls) -> None:
         """Set up the tests."""
-        cls.explanations = _get_test_shap_explanations()
+        cls.test_pipeline = _get_test_morgan_rf_pipeline()
+        cls.test_pipeline.fit(TEST_SMILES, CONTAINS_OX)
+        cls.test_explainer = SHAPTreeExplainer(cls.test_pipeline)
+        cls.test_explanations = cls.test_explainer.explain(TEST_SMILES)
 
     def test_grid_with_shap_atom_weights(self) -> None:
         """Test grid with SHAP atom weights."""
-        for explanation in self.explanations:
+        for explanation in self.test_explanations:
             self.assertTrue(explanation.is_valid())
             self.assertIsInstance(explanation.atom_weights, np.ndarray)