diff --git a/components/sceneutil/lightmanager.cpp b/components/sceneutil/lightmanager.cpp
index 43f11cf00..ba2f8c510 100644
--- a/components/sceneutil/lightmanager.cpp
+++ b/components/sceneutil/lightmanager.cpp
@@ -164,7 +164,7 @@ namespace SceneUtil
             mStateSetCache.clear();
     }
 
-    void LightManager::addLight(LightSource* lightSource, osg::Matrixf worldMat)
+    void LightManager::addLight(LightSource* lightSource, const osg::Matrixf& worldMat)
     {
         LightSourceTransform l;
         l.mLightSource = lightSource;
diff --git a/components/sceneutil/lightmanager.hpp b/components/sceneutil/lightmanager.hpp
index ecee873e8..89ffc1305 100644
--- a/components/sceneutil/lightmanager.hpp
+++ b/components/sceneutil/lightmanager.hpp
@@ -77,7 +77,7 @@ namespace SceneUtil
         void update();
 
         // Called automatically by the LightSource's UpdateCallback
-        void addLight(LightSource* lightSource, osg::Matrixf worldMat);
+        void addLight(LightSource* lightSource, const osg::Matrixf& worldMat);
 
         struct LightSourceTransform
         {