diff --git a/physics/physics_feeders/us_base_physics_parameters.py b/physics/physics_feeders/us_base_physics_parameters.py
index 28f1c8fc..787b6330 100644
--- a/physics/physics_feeders/us_base_physics_parameters.py
+++ b/physics/physics_feeders/us_base_physics_parameters.py
@@ -69,8 +69,6 @@ class UsBasePhysicsParameters:
             material.no_mass = 'no_mass' in material_lib
             if 'thermal_resistance' in material_lib:
               material.thermal_resistance_m2k_w = material_lib['thermal_resistance']['#text']
-            else:
-              material.thermal_resistance_m2k_w = None
             layer.material = material
             thermal_boundary.layers.append(layer)
           for opening in thermal_boundary.thermal_openings: