diff --git a/hysop/operator/diffusion.py b/hysop/operator/diffusion.py
index 4ec713bb085d3a1d723728ef90bde9a3a4726642..cc31bd226e4f36d2af66f7741392eda630bde9e6 100644
--- a/hysop/operator/diffusion.py
+++ b/hysop/operator/diffusion.py
@@ -13,7 +13,10 @@ from hysop.parameters.scalar_parameter import ScalarParameter
 from hysop.operator.base.spectral_operator import SpectralComputationalGraphNodeFrontend
 from hysop.backend.host.python.operator.diffusion   import PythonDiffusion
 from hysop.backend.device.opencl.operator.diffusion import OpenClDiffusion
-from hysop.backend.host.fortran.operator.diffusion  import DiffusionFFTW
+try:
+    from hysop.backend.host.fortran.operator.diffusion  import DiffusionFFTW
+except ImportError:
+    DiffusionFFTW = None
 
 class Diffusion(SpectralComputationalGraphNodeFrontend):
     """
diff --git a/hysop/operator/poisson.py b/hysop/operator/poisson.py
index 91208a94ee07199afda36c22ca9a9b356103aef0..7f60fc3eaffcb2d69b23281481d7c0791c2c9949 100644
--- a/hysop/operator/poisson.py
+++ b/hysop/operator/poisson.py
@@ -12,7 +12,10 @@ from hysop.topology.cartesian_descriptor import CartesianTopologyDescriptors
 from hysop.operator.base.spectral_operator import SpectralComputationalGraphNodeFrontend
 from hysop.backend.host.python.operator.poisson import PythonPoisson
 from hysop.backend.device.opencl.operator.poisson import OpenClPoisson
-from hysop.backend.host.fortran.operator.poisson  import PoissonFFTW
+try:
+    from hysop.backend.host.fortran.operator.poisson  import PoissonFFTW
+except ImportError:
+    PoissonFFTW = None
 
 class Poisson(SpectralComputationalGraphNodeFrontend):
     """
diff --git a/hysop/operator/poisson_curl.py b/hysop/operator/poisson_curl.py
index 1fc61f707f56139b36095f62772627d54c62a0bb..837b52817cf23f1dd5f00fa6edcc9491e3e1db6f 100644
--- a/hysop/operator/poisson_curl.py
+++ b/hysop/operator/poisson_curl.py
@@ -10,9 +10,12 @@ from hysop.fields.continuous_field import Field
 from hysop.topology.cartesian_descriptor import CartesianTopologyDescriptors
 
 from hysop.operator.base.spectral_operator import SpectralComputationalGraphNodeFrontend
-from hysop.backend.host.fortran.operator.poisson_curl  import FortranPoissonCurl
 from hysop.backend.host.python.operator.poisson_curl   import PythonPoissonCurl
 from hysop.backend.device.opencl.operator.poisson_curl import OpenClPoissonCurl
+try:
+    from hysop.backend.host.fortran.operator.poisson_curl  import FortranPoissonCurl
+except ImportError:
+    FortranPoissonCurl = None
 
 class PoissonCurl(SpectralComputationalGraphNodeFrontend):
     """