diff --git a/building_boundary/core/segmentation.py b/building_boundary/core/segmentation.py
index cc33c45..bcfe669 100644
--- a/building_boundary/core/segmentation.py
+++ b/building_boundary/core/segmentation.py
@@ -277,7 +277,7 @@ def boundary_segmentation(points, distance):
     shift = np.min(points_shifted, axis=0)
     points_shifted -= shift
 
-    mask = np.ones(len(points_shifted), dtype=np.bool)
+    mask = np.ones(len(points_shifted), dtype=bool)
     indices = np.arange(len(points_shifted))
 
     segments = []
diff --git a/building_boundary/shapes/alpha_shape.py b/building_boundary/shapes/alpha_shape.py
index 577c26d..701c43b 100644
--- a/building_boundary/shapes/alpha_shape.py
+++ b/building_boundary/shapes/alpha_shape.py
@@ -14,10 +14,10 @@
     from CGAL.CGAL_Alpha_shape_2 import Alpha_shape_2
     from CGAL.CGAL_Alpha_shape_2 import REGULAR
     CGAL_AVAILABLE = True
-    cascaded_union = None
+    unary_union = None
     Delaunay = None
 except ImportError:
-    from shapely.ops import cascaded_union
+    from shapely.ops import unary_union
     from scipy.spatial import Delaunay
     CGAL_AVAILABLE = False
     Point_2 = None
@@ -110,7 +110,11 @@ def triangle_geometry(triangle):
     # Semiperimeter of triangle
     s = (a + b + c) / 2.0
     # Area of triangle by Heron's formula
-    area = math.sqrt(s * (s - a) * (s - b) * (s - c))
+    area = 0
+    try:
+        area = math.sqrt(s * (s - a) * (s - b) * (s - c))
+    except ValueError:
+        pass
     if area != 0:
         circum_r = (a * b * c) / (4.0 * area)
     else:
@@ -144,9 +148,9 @@ def alpha_shape_python(points, alpha):
             if circum_r < 1.0 / alpha:
                 triangles.append(Polygon(points[t]))
 
-    alpha_shape = cascaded_union(triangles)
+    alpha_shape = unary_union(triangles)
     if type(alpha_shape) == MultiPolygon:
-        alpha_shape = MultiPolygon([Polygon(s.exterior) for s in alpha_shape])
+        alpha_shape = MultiPolygon([Polygon(s.exterior) for s in alpha_shape.geoms])
     else:
         alpha_shape = Polygon(alpha_shape.exterior)
 
diff --git a/building_boundary/shapes/fit.py b/building_boundary/shapes/fit.py
index 39ce9d8..92ee088 100644
--- a/building_boundary/shapes/fit.py
+++ b/building_boundary/shapes/fit.py
@@ -7,7 +7,7 @@
 import numpy as np
 from scipy.spatial import ConvexHull
 from shapely.geometry import Polygon
-from shapely.ops import cascaded_union
+from shapely.ops import unary_union
 
 import concave_hull
 
@@ -45,10 +45,11 @@ def compute_shape(points, alpha=None, k=None):
         if k is not None:
             boundary_points = concave_hull.compute(points, k, True)
             shape_ch = Polygon(boundary_points).buffer(0)
-            shape = cascaded_union([shape, shape_ch])
+            if shape_ch.is_valid:
+                shape = unary_union([shape, shape_ch])
 
         if type(shape) != Polygon:
-            shape = max(shape, key=lambda s: s.area)
+            shape = max(shape.geoms, key=lambda s: s.area)
 
     elif k is not None:
         boundary_points = concave_hull.compute(points, k, True)