diff --git a/src/osgPlugins/stl/ReaderWriterSTL.cpp b/src/osgPlugins/stl/ReaderWriterSTL.cpp
index 2665c971a..d17d5a323 100644
--- a/src/osgPlugins/stl/ReaderWriterSTL.cpp
+++ b/src/osgPlugins/stl/ReaderWriterSTL.cpp
@@ -346,7 +346,7 @@ private:
             osg::Matrix m_mat;
             bool m_dontSaveNormals;
 
-            inline void operator () (const osg::Vec3& _v1, const osg::Vec3& _v2, const osg::Vec3& _v3, bool treatVertexDataAsTemporary)
+            inline void operator () (const osg::Vec3& _v1, const osg::Vec3& _v2, const osg::Vec3& _v3, bool /*treatVertexDataAsTemporary*/)
             {
                 osg::Vec3 v1 = _v1 * m_mat;
                 osg::Vec3 v2 = _v2 * m_mat;