diff --git a/quantile_forest/_quantile_forest_fast.pyx b/quantile_forest/_quantile_forest_fast.pyx
index e2928bf..690dd4b 100755
--- a/quantile_forest/_quantile_forest_fast.pyx
+++ b/quantile_forest/_quantile_forest_fast.pyx
@@ -885,6 +885,7 @@ cdef class QuantileForest:
                         if train_indices[k].size() == 0:
                             continue
 
+                        # Clear list of training target values.
                         leaf_samples.clear()
 
                         # Get training target values associated with indices.
diff --git a/quantile_forest/tests/test_quantile_forest.py b/quantile_forest/tests/test_quantile_forest.py
index eaac0c3..f01e6aa 100755
--- a/quantile_forest/tests/test_quantile_forest.py
+++ b/quantile_forest/tests/test_quantile_forest.py
@@ -680,6 +680,7 @@ def check_quantile_ranks(name):
     assert y_ranks.shape == (X_test.shape[0], 2)
     assert np.all(y_ranks >= 0)
     assert np.all(y_ranks <= 1)
+    assert np.all(y_ranks[:, 0] < y_ranks[:, 1])
 
 
 @pytest.mark.parametrize("name", FOREST_REGRESSORS)