diff --git a/invesalius/data/viewer_volume.py b/invesalius/data/viewer_volume.py
index df2e86f..0a849dc 100755
--- a/invesalius/data/viewer_volume.py
+++ b/invesalius/data/viewer_volume.py
@@ -19,6 +19,7 @@
 
 import sys
 
+import numpy
 import wx
 import vtk
 from vtk.wx.wxVTKRenderWindowInteractor import wxVTKRenderWindowInteractor
--
libgit2 0.21.2