diff --git a/src/object.cc b/src/object.cc
index 57db9c0..3b0bdf6 100644
--- a/src/object.cc
+++ b/src/object.cc
@@ -85,13 +85,12 @@ Object::Normal(const Vector4& p)
  * charles::Object::ToObjectSpace --
  */
 Ray
-Object::ToObjectSpace(const Ray& ray)
+Object::ToObjectSpace(Ray ray)
     const
 {
-    Ray objRay(ray);
-    objRay.origin = mTranslation * objRay.origin;
-    objRay.direction = mTranslation * objRay.direction;
-    return objRay;
+    ray.origin = mTranslation * ray.origin;
+    ray.direction = mTranslation * ray.direction;
+    return ray;
 }
 
 
diff --git a/src/object.hh b/src/object.hh
index 6696d72..9bb47a7 100644
--- a/src/object.hh
+++ b/src/object.hh
@@ -59,7 +59,7 @@ protected:
 
 private:
     /** Convert `ray` to object space from global space. */
-    basics::Ray ToObjectSpace(const basics::Ray& ray) const;
+    basics::Ray ToObjectSpace(basics::Ray ray) const;
 
     /** Convert `v` to object space from global space. */
     basics::Vector4 ToObjectSpace(const basics::Vector4& v) const;