diff --git a/FemDesign.Core/Materials/MaterialBase.cs b/FemDesign.Core/Materials/MaterialBase.cs
index 3b81b53de..d8d09e411 100644
--- a/FemDesign.Core/Materials/MaterialBase.cs
+++ b/FemDesign.Core/Materials/MaterialBase.cs
@@ -15,7 +15,7 @@ public partial class MaterialBase
         public double Mass
         {
             get { return _mass; }
-            set { RestrictedDouble.NonNegMax_1e20(value); } // non_neg_max_1e20
+            set { _mass = RestrictedDouble.NonNegMax_1e20(value); } // non_neg_max_1e20
         }
 
         [XmlAttribute("E_0")]