Index: OpenSceneGraph/trunk/src/osg/Referenced.cpp
===================================================================
--- OpenSceneGraph/trunk/src/osg/Referenced.cpp (revision 9343)
+++ OpenSceneGraph/trunk/src/osg/Referenced.cpp (revision 9549)
@@ -310,5 +310,5 @@
 }
 
-void Referenced::addObserver(Observer* observer)
+void Referenced::addObserver(Observer* observer) const
 {
 #if defined(_OSG_REFERENCED_USE_ATOMIC_OPERATIONS)
@@ -338,5 +338,5 @@
 }
 
-void Referenced::removeObserver(Observer* observer)
+void Referenced::removeObserver(Observer* observer) const
 {
 #if defined(_OSG_REFERENCED_USE_ATOMIC_OPERATIONS)