diff --git a/hysop/simulation.py b/hysop/simulation.py
index d951cb7f376491b19bd7d214c8da285cf1c9a1ac..9b1bf18b2c584f2def5935fda1d612a40da5f92d 100644
--- a/hysop/simulation.py
+++ b/hysop/simulation.py
@@ -448,6 +448,8 @@ class Simulation:
             io_params = kwds.pop('io_params')
         _params = ()
         for p in params:
+            if p is None:
+                continue
             for (_, param) in p.iterviews():
                 _params += (param,)
         params = _params