diff --git a/neurom/features/morphology.py b/neurom/features/morphology.py
index 5abac73f..bc7e096a 100644
--- a/neurom/features/morphology.py
+++ b/neurom/features/morphology.py
@@ -643,7 +643,7 @@ def aspect_ratio(morph, neurite_type=NeuriteType.all, projection_plane="xy"):
         The aspect ratio feature of the morphology points.
     """
     projected_points = _unique_projected_points(morph, projection_plane, neurite_type)
-    return [] if len(projected_points) == 0 else morphmath.aspect_ratio(projected_points)
+    return np.nan if len(projected_points) == 0 else morphmath.aspect_ratio(projected_points)
 
 
 @feature(shape=())
@@ -663,7 +663,7 @@ def circularity(morph, neurite_type=NeuriteType.all, projection_plane="xy"):
         The circularity of the morphology points.
     """
     projected_points = _unique_projected_points(morph, projection_plane, neurite_type)
-    return [] if len(projected_points) == 0 else morphmath.circularity(projected_points)
+    return np.nan if len(projected_points) == 0 else morphmath.circularity(projected_points)
 
 
 @feature(shape=())
@@ -683,4 +683,4 @@ def shape_factor(morph, neurite_type=NeuriteType.all, projection_plane="xy"):
         The shape factor of the morphology points.
     """
     projected_points = _unique_projected_points(morph, projection_plane, neurite_type)
-    return [] if len(projected_points) == 0 else morphmath.shape_factor(projected_points)
+    return np.nan if len(projected_points) == 0 else morphmath.shape_factor(projected_points)
diff --git a/tests/features/test_get_features.py b/tests/features/test_get_features.py
index 20372b95..ae731323 100644
--- a/tests/features/test_get_features.py
+++ b/tests/features/test_get_features.py
@@ -916,6 +916,7 @@ def test_aspect_ratio():
         0.731076,
         decimal=6
     )
+    assert np.isnan(features.get("aspect_ratio", morph, neurite_type=nm.NeuriteType.custom5))
 
 
 def test_circularity():
@@ -942,6 +943,7 @@ def test_circularity():
         0.730983,
         decimal=6
     )
+    assert np.isnan(features.get("circularity", morph, neurite_type=nm.NeuriteType.custom5))
 
 
 def test_shape_factor():
@@ -968,3 +970,4 @@ def test_shape_factor():
         0.364678,
         decimal=6
     )
+    assert np.isnan(features.get("shape_factor", morph, neurite_type=nm.NeuriteType.custom5))