diff --git a/Packages/nadena.dev.modular-avatar/Editor/MergeArmatureHook.cs b/Packages/nadena.dev.modular-avatar/Editor/MergeArmatureHook.cs
index 419ab9c6..3888c342 100644
--- a/Packages/nadena.dev.modular-avatar/Editor/MergeArmatureHook.cs
+++ b/Packages/nadena.dev.modular-avatar/Editor/MergeArmatureHook.cs
@@ -403,6 +403,34 @@ namespace nadena.dev.modular_avatar.core.editor
                 }
             }
 
+            if (mergedSrcBone == newParent
+                && (
+                    Vector3.SqrMagnitude(mergedSrcBone.transform.localScale - src.transform.localScale) > 0.00001f
+                    || Quaternion.Angle(mergedSrcBone.transform.localRotation, src.transform.localRotation) > 0.00001f
+                    || Vector3.SqrMagnitude(mergedSrcBone.transform.localPosition - src.transform.localPosition) > 0.00001f
+                )
+                && src.GetComponent<IConstraint>() != null
+            )
+            {
+                // Constraints are sensitive to changes in local reference frames in some cases. In this case we'll
+                // inject a dummy object in between in order to retain the local parent scale of the retargeted bone.
+                var objName = src.gameObject.name + "$ConstraintRef " + Guid.NewGuid();
+                
+                var constraintScaleRef = new GameObject(objName);
+                constraintScaleRef.transform.SetParent(src.transform.parent);
+                constraintScaleRef.transform.localPosition = Vector3.zero;
+                constraintScaleRef.transform.localRotation = Quaternion.identity;
+                constraintScaleRef.transform.localScale = Vector3.one;
+                
+                constraintScaleRef.transform.SetParent(newParent.transform, true);
+                mergedSrcBone = constraintScaleRef;
+                
+                BoneDatabase.AddMergedBone(mergedSrcBone.transform);
+                BoneDatabase.RetainMergedBone(mergedSrcBone.transform);
+                PathMappings.MarkTransformLookthrough(mergedSrcBone);
+                thisPassAdded.Add(mergedSrcBone.transform);
+            }
+
             src.transform.SetParent(mergedSrcBone.transform, true);
             if (config.mangleNames)
             {