diff --git a/face3d/mesh_cython/light.py b/face3d/mesh_cython/light.py
index b448676..661c2be 100644
--- a/face3d/mesh_cython/light.py
+++ b/face3d/mesh_cython/light.py
@@ -9,7 +9,7 @@
 from __future__ import print_function
 
 import numpy as np
-import mesh_core_cython
+from . import mesh_core_cython
 
 def get_normal(vertices, triangles):
     ''' calculate normal direction in each vertex