diff --git a/Assets/VRM/Runtime/IO/MaterialIO/URP/Import/UrpVrmMaterialDescriptorGenerator.cs b/Assets/VRM/Runtime/IO/MaterialIO/URP/Import/UrpVrmMaterialDescriptorGenerator.cs
index a0aa70f6a..10da02bdd 100644
--- a/Assets/VRM/Runtime/IO/MaterialIO/URP/Import/UrpVrmMaterialDescriptorGenerator.cs
+++ b/Assets/VRM/Runtime/IO/MaterialIO/URP/Import/UrpVrmMaterialDescriptorGenerator.cs
@@ -9,8 +9,8 @@ namespace VRM
     {
         private readonly glTF_VRM_extensions _vrm;
 
-        public UrpGltfPbrMaterialImporter PbrMaterialImporter { get; }
-        public UrpGltfDefaultMaterialImporter DefaultMaterialImporter { get; }
+        public UrpGltfPbrMaterialImporter PbrMaterialImporter { get; } = new();
+        public UrpGltfDefaultMaterialImporter DefaultMaterialImporter { get; } = new();
 
         public UrpVrmMaterialDescriptorGenerator(glTF_VRM_extensions vrm)
         {
diff --git a/Assets/VRM10/Runtime/IO/Material/URP/Import/UrpVrm10MaterialDescriptorGenerator.cs b/Assets/VRM10/Runtime/IO/Material/URP/Import/UrpVrm10MaterialDescriptorGenerator.cs
index 4717b195f..f3ae462a2 100644
--- a/Assets/VRM10/Runtime/IO/Material/URP/Import/UrpVrm10MaterialDescriptorGenerator.cs
+++ b/Assets/VRM10/Runtime/IO/Material/URP/Import/UrpVrm10MaterialDescriptorGenerator.cs
@@ -7,8 +7,8 @@ namespace UniVRM10
 {
     public sealed class UrpVrm10MaterialDescriptorGenerator : IMaterialDescriptorGenerator
     {
-        public UrpGltfPbrMaterialImporter PbrMaterialImporter { get; }
-        public UrpGltfDefaultMaterialImporter DefaultMaterialImporter { get; }
+        public UrpGltfPbrMaterialImporter PbrMaterialImporter { get; } = new();
+        public UrpGltfDefaultMaterialImporter DefaultMaterialImporter { get; } = new();
 
         public MaterialDescriptor Get(GltfData data, int i)
         {