diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureIO/TextureExporter.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureIO/TextureExporter.cs
index ca73855ef..486bdece0 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureIO/TextureExporter.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/TextureIO/TextureExporter.cs
@@ -45,6 +45,10 @@ namespace UniGLTF
         /// <returns></returns>
         public int GetTextureIndex(Texture src, glTFTextureTypes textureType)
         {
+            if (src == null)
+            {
+                return -1;
+            }
             return m_exportMap[new ExportKey(src, textureType)];
         }
 
diff --git a/Assets/VRM/Runtime/IO/VRMExporter.cs b/Assets/VRM/Runtime/IO/VRMExporter.cs
index 980cef846..a24c3e240 100644
--- a/Assets/VRM/Runtime/IO/VRMExporter.cs
+++ b/Assets/VRM/Runtime/IO/VRMExporter.cs
@@ -137,7 +137,7 @@ namespace VRM
                     VRM.meta.title = meta.Title;
                     if (meta.Thumbnail != null)
                     {
-                        VRM.meta.texture = TextureExporter.ExportTexture(glTF, glTF.buffers.Count - 1, meta.Thumbnail);
+                        VRM.meta.texture = TextureManager.ExportSRGB(meta.Thumbnail);
                     }
 
                     // ussage permission
@@ -200,7 +200,7 @@ namespace VRM
             // materials
             foreach (var m in Materials)
             {
-                VRM.materialProperties.Add(VRMMaterialExporter.CreateFromMaterial(m, TextureManager.GetTextureIndex));
+                VRM.materialProperties.Add(VRMMaterialExporter.CreateFromMaterial(m, TextureManager));
             }
 
             // Serialize VRM
diff --git a/Assets/VRM/Runtime/IO/VRMMaterialExporter.cs b/Assets/VRM/Runtime/IO/VRMMaterialExporter.cs
index 2b955cb95..0b49c6b90 100644
--- a/Assets/VRM/Runtime/IO/VRMMaterialExporter.cs
+++ b/Assets/VRM/Runtime/IO/VRMMaterialExporter.cs
@@ -107,7 +107,7 @@ namespace VRM
             // "Queue",
         };
 
-        public static glTF_VRM_Material CreateFromMaterial(Material m, Func<Texture, glTFTextureTypes, int> getTextureIndex)
+        public static glTF_VRM_Material CreateFromMaterial(Material m, TextureExporter textureExporter)
         {
             var material = new glTF_VRM_Material
             {
@@ -160,12 +160,10 @@ namespace VRM
                                 var texture = m.GetTexture(kv.Key);
                                 if (texture != null)
                                 {
-                                    var textureType = glTFTextureTypes.SRGB;
-                                    if (kv.Key == "_BumpMap")
-                                    {
-                                        textureType = glTFTextureTypes.Normal;
-                                    }
-                                    var value = getTextureIndex(texture, textureType);
+                                    var value = kv.Key == "_BumpMap"
+                                        ? textureExporter.ExportNormal(texture)
+                                        : textureExporter.ExportSRGB(texture)
+                                        ;
                                     if (value == -1)
                                     {
                                         Debug.LogFormat("not found {0}", texture.name);