diff --git a/src/pybind_example/labelled_tetrahedral_mesh.py b/src/pybind_example/labelled_tetrahedral_mesh.py
index ce7b8b718f18557c14d2100e8b3cda59180fe63e..4699c0f0ec24f4d76310cb5c72baf992000b14ed 100644
--- a/src/pybind_example/labelled_tetrahedral_mesh.py
+++ b/src/pybind_example/labelled_tetrahedral_mesh.py
@@ -1,8 +1,10 @@
+from typing import Iterable, Optional
+
 import numpy as np
 
 from ._wrp import LabelledTetrahedralMesh, make_tetrahedron
 from ._wrp import build_cgal_image as _build_cgal_image
 
 
-def build_cgal_image(img: np.ndarray) -> bool:
-    return _build_cgal_image(img.ravel().astype(np.uint16), img.shape, [1., 1., 1.])
+def build_cgal_image(img: np.ndarray, voxelsize: Optional[Iterable[float]]=(1., 1., 1.)) -> bool:
+    return _build_cgal_image(img.ravel().astype(np.uint16), img.shape, voxelsize)
diff --git a/tests/test_cgal_image.py b/tests/test_cgal_image.py
index 4f60f143729809f4e0fff34037e089bc15ed43a9..9506048491d2ef6b7bd1eda014fdbed76da616fb 100644
--- a/tests/test_cgal_image.py
+++ b/tests/test_cgal_image.py
@@ -13,9 +13,11 @@ class TestCgalImage(unittest.TestCase):
         self.image[:, :4, :4] = 2
         self.image[:, 4:, :4] = 3
 
+        self.voxelsize = [0.5, 0.5, 1]
+
     def tearDown(self):
         pass
 
     def test_cgal_image(self):
-        res = build_cgal_image(self.image)
+        res = build_cgal_image(self.image, voxelsize=self.voxelsize)
         assert res == 0