diff --git a/meshmode/discretization/visualization.py b/meshmode/discretization/visualization.py
index 2d908b8f8f6c2f38f0f0dcccfc9cb2c338e5e2c3..5e20d2216aea16211fcdc7aba6b109d4bed24c05 100644
--- a/meshmode/discretization/visualization.py
+++ b/meshmode/discretization/visualization.py
@@ -420,6 +420,7 @@ class Visualizer(object):
     @property
     @memoize_method
     def _vtk_lagrange_connectivity(self):
+        assert self.is_equidistant
         return VTKLagrangeConnectivity(self.connection)
 
     def write_high_order_vtk_file(self, file_name, names_and_fields,