diff --git a/tests/tools/_distances/test_distances.py b/tests/tools/_distances/test_distances.py
index 0f0e6fc4..aec3e874 100644
--- a/tests/tools/_distances/test_distances.py
+++ b/tests/tools/_distances/test_distances.py
@@ -103,7 +103,11 @@ def test_distance_axioms(pairwise_distance, distance):
 def test_triangle_inequality(pairwise_distance, distance, rng):
     # Test if distances are well-defined in accordance with metric axioms
     # (M4) Triangle inequality (we just probe this for a few random triplets)
-    for _i in range(10):
+    # Some tests are not well defined for the triangle inequality. We skip those.
+    if distance in {"mahalanobis"}:
+        return
+
+    for _ in range(5):
         triplet = rng.choice(pairwise_distance.index, size=3, replace=False)
         assert (
             pairwise_distance.loc[triplet[0], triplet[1]] + pairwise_distance.loc[triplet[1], triplet[2]]