diff --git a/components/stereo/frustum.hpp b/components/stereo/frustum.hpp
index 35e3adf95a..56740c125a 100644
--- a/components/stereo/frustum.hpp
+++ b/components/stereo/frustum.hpp
@@ -2,10 +2,7 @@
 #define STEREO_FRUSTUM_H
 
 #include <osg/BoundingBox>
-#include <osg/Camera>
 #include <osg/Matrix>
-#include <osg/StateSet>
-#include <osg/Vec3>
 
 #include <array>
 #include <map>
@@ -13,6 +10,7 @@
 
 namespace osg
 {
+    class Camera;
     class FrameBufferObject;
     class Texture2D;
     class Texture2DMultisample;
@@ -24,7 +22,7 @@ namespace osgViewer
     class Viewer;
 }
 
-namespace usgUtil
+namespace osgUtil
 {
     class CullVisitor;
 }