diff --git a/Assets/VRM10/Runtime/IO/Model/ModelExporter.cs b/Assets/VRM10/Runtime/IO/Model/ModelExporter.cs
index b7f3302e9..d35307261 100644
--- a/Assets/VRM10/Runtime/IO/Model/ModelExporter.cs
+++ b/Assets/VRM10/Runtime/IO/Model/ModelExporter.cs
@@ -307,7 +307,17 @@ namespace UniVRM10
                 skin.Root = nodes[skinnedMeshRenderer.rootBone.gameObject];
             }
 
-            skin.Joints = skinnedMeshRenderer.bones.Select(x => nodes[x.gameObject]).ToList();
+            skin.Joints = skinnedMeshRenderer.bones.Select(x =>
+            {
+                if (x != null)
+                {
+                    return nodes[x.gameObject];
+                }
+                else
+                {
+                    return null;
+                }
+            }).ToList();
             return skin;
         }
 
diff --git a/Assets/VRM10/Runtime/IO/Vrm10Exporter.cs b/Assets/VRM10/Runtime/IO/Vrm10Exporter.cs
index 71c1aef0c..95d68cddc 100644
--- a/Assets/VRM10/Runtime/IO/Vrm10Exporter.cs
+++ b/Assets/VRM10/Runtime/IO/Vrm10Exporter.cs
@@ -93,7 +93,18 @@ namespace UniVRM10
                     {
                         gltfSkin = new glTFSkin()
                         {
-                            joints = skin.Joints.Select(joint => nodes.IndexOfThrow(joint)).ToArray()
+                            joints = skin.Joints.Select(joint =>
+                            {
+                                var index = nodes.IndexOf(joint);
+                                if (index < 0)
+                                {
+                                    return 0;
+                                }
+                                else
+                                {
+                                    return index;
+                                }
+                            }).ToArray()
                         };
                         if (skin.InverseMatrices == null)
                         {