diff --git a/Assets/VRM10/Runtime/FastSpringBone/System/UpdateFastSpringBoneJob.cs b/Assets/VRM10/Runtime/FastSpringBone/System/UpdateFastSpringBoneJob.cs
index 7e7352a16..8da06bef0 100644
--- a/Assets/VRM10/Runtime/FastSpringBone/System/UpdateFastSpringBoneJob.cs
+++ b/Assets/VRM10/Runtime/FastSpringBone/System/UpdateFastSpringBoneJob.cs
@@ -156,7 +156,7 @@ namespace UniVRM10.FastSpringBones.System
             BlittableLogic logic,
             ref Vector3 nextTail)
         {
-            var P = worldTail - worldPosition;
+            var P = (worldTail - worldPosition).normalized;
             var Q = headTransform.position - worldPosition;
             var dot = Vector3.Dot(P, Q);
             if (dot <= 0)