diff --git a/HySoP/hysop/operator/diffusion.py b/HySoP/hysop/operator/diffusion.py
index 80f52a89c8b01409fda4d8ef93479302f14306d4..c1eb3ab8ec9a8f2119342ae1486fba1fe7b0eb23 100644
--- a/HySoP/hysop/operator/diffusion.py
+++ b/HySoP/hysop/operator/diffusion.py
@@ -9,6 +9,7 @@ from parmepy.operator.continuous import Operator
 from parmepy.f2py import fftw2py
 from parmepy.operator.discrete.diffusion_fft import DiffusionFFT
 from parmepy.constants import debug
+from parmepy.methods_keys import SpaceDiscretisation, GhostUpdate
 import numpy as np
 
 
@@ -35,7 +36,8 @@ class Diffusion(Operator):
         """
         # The only available method at the time is fftw
         if method is None:
-            method = 'fftw'
+            method = {SpaceDiscretisation: 'fftw', GhostUpdate: True}
+
         ## input/output field, solution of the problem
         self.vorticity = vorticity
         ## Global resolution for vorticity
@@ -50,7 +52,7 @@ class Diffusion(Operator):
 
     def discretize(self):
         # The only available solver is fftw
-        if self.method is not 'fftw':
+        if self.method[SpaceDiscretisation] is not 'fftw':
             print self.method
             raise AttributeError("Method not yet implemented.")
 
diff --git a/HySoP/hysop/operator/discrete/differential.py b/HySoP/hysop/operator/discrete/differential.py
index 514a3d8077a6a92ba57dc01405e2c429f4fa9935..52a16ddee97f6b42d60f3f2d1441627f2d5f5582 100644
--- a/HySoP/hysop/operator/discrete/differential.py
+++ b/HySoP/hysop/operator/discrete/differential.py
@@ -24,8 +24,7 @@ class Differential(DiscreteOperator):
     ##     return object.__new__(cls, *args, **kw)
 
     @debug
-    def __init__(self, invar, outvar,
-                 method={SpaceDiscretisation: FD_C_4, GhostUpdate: True}):
+    def __init__(self, invar, outvar, method=None):
         """
         @param[in] invar : input field
         @param[in,out] outvar : Grad of the input field.
@@ -36,6 +35,8 @@ class Differential(DiscreteOperator):
         """
         self.invar = invar
         self.outvar = outvar
+        if method is None:
+            method = {SpaceDiscretisation: FD_C_4, GhostUpdate: True}
         DiscreteOperator.__init__(self, [self.invar, self.outvar],
                                   method=method)
         self.input = [self.invar]
diff --git a/HySoP/hysop/operator/discrete/discrete.py b/HySoP/hysop/operator/discrete/discrete.py
index a752db902e728422419f6ccb33f1cb1fe4b6e96b..96fe01654db125aba97bc0cee186d5b105d6c581 100644
--- a/HySoP/hysop/operator/discrete/discrete.py
+++ b/HySoP/hysop/operator/discrete/discrete.py
@@ -5,6 +5,7 @@ Abstract interface for discrete operators.
 from abc import ABCMeta, abstractmethod
 from parmepy.constants import debug
 from parmepy.tools.timers import Timer, ManualFunctionTimer
+from parmepy.methods_keys import GhostUpdate
 
 
 class DiscreteOperator(object):
@@ -40,6 +41,8 @@ class DiscreteOperator(object):
         if method is None:
             method = {}
         self.method = method
+        if not GhostUpdate in method:
+            method[GhostUpdate] = True
         self.name = self.__class__.__name__
         ## Object to store computational times of lower level functions
         self.timer = Timer(self)