diff --git a/_tools/vtk/saveMagnetization.py b/_tools/vtk/saveMagnetization.py
index 2e62e764bd5816b465cdaf99b6b66147b843ac49..e12b9413d2b8f5393b263c43b988568ffbcd2a1d 100644
--- a/_tools/vtk/saveMagnetization.py
+++ b/_tools/vtk/saveMagnetization.py
@@ -10,7 +10,11 @@ def SaveMagnetization(filename, mesh, m, label="m"):
   content += Mesh2VTK(mesh)
   content += Mag2VTK(mesh, m, label)
   
-  output = open(filename + ".vtk", "w")
+  ext = ".vtk"
+  if(filename[-4:] == ext):
+    ext = ""
+
+  output = open(filename + ext, "w")
   output.write(content)
   output.close()