diff --git a/invesalius/data/surface.py b/invesalius/data/surface.py
index 314caf5..cb3265e 100644
--- a/invesalius/data/surface.py
+++ b/invesalius/data/surface.py
@@ -235,7 +235,7 @@ class SurfaceManager():
         mapper = vtk.vtkPolyDataMapper()
         mapper.SetInput(normals.GetOutput())
         mapper.ScalarVisibilityOff()
-	mapper.ImmediateModeRenderingOn() # improve performance
+        mapper.ImmediateModeRenderingOn() # improve performance
 
         actor = vtk.vtkActor()
         actor.SetMapper(mapper)
@@ -473,7 +473,7 @@ class SurfaceManager():
         mapper = vtk.vtkPolyDataMapper()
         mapper.SetInput(stripper.GetOutput())
         mapper.ScalarVisibilityOff()
-	mapper.ImmediateModeRendering() # improve performance
+        mapper.ImmediateModeRenderingOn() # improve performance
 
         # Represent an object (geometry & properties) in the rendered scene
         actor = vtk.vtkActor()
--
libgit2 0.21.2