diff --git a/examples/osgvolume/osgvolume.cpp b/examples/osgvolume/osgvolume.cpp
index e444db521..29efa4e3f 100644
--- a/examples/osgvolume/osgvolume.cpp
+++ b/examples/osgvolume/osgvolume.cpp
@@ -312,7 +312,7 @@ public:
         errorMessage(),
         maximumTextureSize(256) {}
 
-    virtual void operator () (osg::GraphicsContext* gc)
+    virtual void operator () (osg::GraphicsContext* /*gc*/)
     {
         OpenThreads::ScopedLock<OpenThreads::Mutex> lock(mutex);