diff --git a/Assets/VRM/UniGLTF/Editor/Serialization/SerializerGenerator.cs b/Assets/VRM/UniGLTF/Editor/Serialization/SerializerGenerator.cs
index 27a81c1bb..e1ea54345 100644
--- a/Assets/VRM/UniGLTF/Editor/Serialization/SerializerGenerator.cs
+++ b/Assets/VRM/UniGLTF/Editor/Serialization/SerializerGenerator.cs
@@ -80,7 +80,7 @@ namespace UniGLTF
                 {"gltf/meshes[]/primitives[]/extras", "if(value.extras!=null && value.extras.targetNames!=null && value.extras.targetNames.Count>0)"},
                 {"gltf/meshes[]/weights", "if(value.weights!=null && value.weights.Length>0)" },
                 {"gltf/materials", "if(value.materials!=null && value.materials.Count>0)" },
-                {"gltf/materials[]/alphaCutoff", "if(!string.IsNullOrEmpty(value.alphaMode))" },
+                {"gltf/materials[]/alphaCutoff", "if(value.alphaMode == \"MASK\")" },
                 {"gltf/nodes", "if(value.nodes!=null && value.nodes.Count>0)" },
                 {"gltf/nodes[]/camera", "if(value.camera!=-1)"},
                 {"gltf/nodes[]/mesh", "if(value.mesh!=-1)"},
diff --git a/Assets/VRM/UniGLTF/Scripts/IO/FormatterExtensionsGltf.g.cs b/Assets/VRM/UniGLTF/Scripts/IO/FormatterExtensionsGltf.g.cs
index 246f88b09..4a4065a66 100644
--- a/Assets/VRM/UniGLTF/Scripts/IO/FormatterExtensionsGltf.g.cs
+++ b/Assets/VRM/UniGLTF/Scripts/IO/FormatterExtensionsGltf.g.cs
@@ -572,7 +572,7 @@ namespace UniGLTF {
             f.Key("alphaMode"); f.GenSerialize(value.alphaMode);
         }
 
-        if(!string.IsNullOrEmpty(value.alphaMode))
+        if(value.alphaMode == "MASK")
         {
             f.Key("alphaCutoff"); f.GenSerialize(value.alphaCutoff);
         }