diff --git a/pyalphashape/AlphaShape.py b/pyalphashape/AlphaShape.py
index e3f8c4f..6d88c89 100644
--- a/pyalphashape/AlphaShape.py
+++ b/pyalphashape/AlphaShape.py
@@ -238,9 +238,9 @@ def contains_point(self, pt: np.ndarray, tol: float = 1e-8) -> bool:
             True if the point lies inside or on the alpha shape; False otherwise.
 
         """
-        assert (
-            self._delaunay is not None
-        ), "Delaunay triangulation must be performed first"
+        if self._delaunay is None or self.perimeter_points is None:
+            return False
+
         # fast hull‐check
         simplex_idx = self._delaunay.find_simplex(pt)
         if simplex_idx < 0:
diff --git a/unit_tests/test_AlphaShape.py b/unit_tests/test_AlphaShape.py
index fdf4084..de76d5d 100644
--- a/unit_tests/test_AlphaShape.py
+++ b/unit_tests/test_AlphaShape.py
@@ -32,6 +32,10 @@ def test_alpha_shape_basic_perimeter():
     assert len(alpha_shape.perimeter_points) > 0
     assert isinstance(alpha_shape.perimeter_edges, list)
 
+def test_contains_point_incomplete():
+    points = np.array([[0, 0], [1, 0]])
+    shape = AlphaShape(points, alpha=0.0)
+    assert not shape.contains_point(np.array([0.5, 0.5]))
 
 def test_contains_point_inside():
     points = np.array([[0, 0], [1, 0], [0.5, 1]])