diff --git a/python/chemiscope/structures/_shapes.py b/python/chemiscope/structures/_shapes.py
index c79c005e2..90d17282d 100644
--- a/python/chemiscope/structures/_shapes.py
+++ b/python/chemiscope/structures/_shapes.py
@@ -147,9 +147,7 @@ def ellipsoid_from_tensor(tensor, scale=1.0, force_positive=False):
     try:
         from scipy.spatial.transform import Rotation
     except ImportError as e:
-        raise RuntimeError(
-            "scipy is required to construct arrow shapes"
-        ) from e
+        raise RuntimeError("scipy is required to construct arrow shapes") from e
     quaternion = Rotation.from_matrix(rotation).as_quat()
 
     return dict(