diff --git a/Assets/VRM10/Runtime/Components/Expression/MaterialValueBindingMerger.cs b/Assets/VRM10/Runtime/Components/Expression/MaterialValueBindingMerger.cs
index 91be2fb2b..f1d8218a0 100644
--- a/Assets/VRM10/Runtime/Components/Expression/MaterialValueBindingMerger.cs
+++ b/Assets/VRM10/Runtime/Components/Expression/MaterialValueBindingMerger.cs
@@ -80,11 +80,14 @@ namespace UniVRM10
                         m_materialMap.Add(binding.MaterialName, item);
                     }
                     var propName = GetProperty(binding.BindType);
-                    item.PropMap.Add(binding.BindType, new PropItem
+                    if (!item.PropMap.ContainsKey(binding.BindType))
                     {
-                        Name = propName,
-                        DefaultValues = item.Material.GetVector(propName),
-                    });
+                        item.PropMap.Add(binding.BindType, new PropItem
+                        {
+                            Name = propName,
+                            DefaultValues = item.Material.GetVector(propName),
+                        });
+                    }
                 }
 
                 foreach (var binding in kv.Value.MaterialUVBindings)
diff --git a/Assets/VRM10/Tests/ExpressionTests.cs b/Assets/VRM10/Tests/ExpressionTests.cs
index a7d617f52..c85838a37 100644
--- a/Assets/VRM10/Tests/ExpressionTests.cs
+++ b/Assets/VRM10/Tests/ExpressionTests.cs
@@ -56,6 +56,7 @@ namespace UniVRM10.Test
             });
             controller.Vrm.Expression.Aa.MaterialColorBindings = src.ToArray();
 
+            // ok if no exception
             var r = new VRM10ControllerRuntime(controller);
         }
     }