diff --git a/Assets/VRM10/Runtime/IO/DictionaryExtensions.cs b/Assets/VRM10/Runtime/IO/DictionaryExtensions.cs
deleted file mode 100644
index 5cddb3de7..000000000
--- a/Assets/VRM10/Runtime/IO/DictionaryExtensions.cs
+++ /dev/null
@@ -1,23 +0,0 @@
-using System.Collections.Generic;
-
-namespace UniVRM10
-{
-    public static class DictionaryExtensions
-    {
-        public static U GetOrDefault<T, U>(this Dictionary<T, U> d, T key)
-        {
-            if(key == null)
-            {
-                return default;
-            }
-
-            if(d.TryGetValue(key, out U value))
-            {
-                return value;;
-            }
-            else{
-                return default;
-            }
-        }
-    }
-}