diff --git a/Packages/VRM10/Runtime/IO/Vrm10Importer.cs b/Packages/VRM10/Runtime/IO/Vrm10Importer.cs
index 3293a901b..f12b274e4 100644
--- a/Packages/VRM10/Runtime/IO/Vrm10Importer.cs
+++ b/Packages/VRM10/Runtime/IO/Vrm10Importer.cs
@@ -3,8 +3,8 @@ using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 using UniGLTF;
+using UniGLTF.Extensions.VRMC_springBone_limit;
 using UniGLTF.Utils;
-using Unity.Mathematics;
 using UnityEngine;
 
 namespace UniVRM10