diff --git a/setup.py b/setup.py
index 76e6556..88f1015 100644
--- a/setup.py
+++ b/setup.py
@@ -19,7 +19,7 @@
                     'scipy>=0.17.0',
                     'scikit-learn>=0.20.0',
                     'matplotlib>=2.0.0',
-                    'vtk>=8.1.0',
+                    'vtk==9.1.0',
                     'nibabel',
                     'pillow',
                     'pandas']